Southwest Fabrication
Caddo Mills, Texas Quality Custom Craftsmanship 7am–3pm Central 469-688-6985 Made in America

GM swap hardware & carbon fiber

Transplanting a GM LS engine in your project and want to retain the factory speedometer and gauge cluster?

Our kit allows you to do just that. We machine tail housing kits that put a 4L60E or 4L80E behind your car's original shifter and cable-driven speedo. And we lay carbon covers so the top of the motor looks like somebody cared.

Classic roadster with a modern LS engine under the hood

Out of the shop

Parts we've built

Cast and machined 4L60E tail housing
Three machined GM tail housings with speedometer bosses
Tail housing kit parts laid out
4L80E tail housing
One-piece carbon fiber LS engine cover
Carbon fiber LS engine cover on the bench
Gelcoat LS engine cover in an engine bay
Carbon fiber bodywork laid up in the shop
Cast and machined 4L60E tail housing
Three machined GM tail housings with speedometer bosses
Tail housing kit parts laid out
4L80E tail housing
One-piece carbon fiber LS engine cover
Carbon fiber LS engine cover on the bench
Gelcoat LS engine cover in an engine bay
Carbon fiber bodywork laid up in the shop
Cast and machined 4L60E tail housing

Tail housing kits

Cable drive off an electronic overdrive, shifter back where it belongs. Keep your gauges. Skip the electric conversion.

Browse housings → One-piece carbon fiber LS engine cover

Carbon fiber covers

One- and two-piece LS covers, aircraft-grade carbon, infused on our own table. Hardware's in the box.

Browse covers → Carbon fiber bodywork laid up in the shop

Custom fabrication

Tooling and one-off composite work when the part you need was never made.

See the work →

Keep your dash

Nothing on the dash gives it away.

Here's what usually happens. You go electronic overdrive, there's no cable drive on the tail housing, so the original speedo is dead. Now you're buying a full electric gauge set and hacking up a dash somebody spent fifty years not hacking up.

Our kits put a mechanical take-off back on the transmission. The gauges that came in the car stay in the car and read true. Fuel injection, overdrive, and an interior that still looks stock.

Featured parts

The four we ship most.

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Get the gears right the first time

Right gears the first time.

Tire diameter and rear gear in, drive and driven tooth count out. No guessing, no second order for the gear you should have bought.

Southwest Fabrication

Machined, laid up and assembled in Caddo Mills, Texas.

Every part on this site comes out of our own shop. Nothing drop-shipped, nothing rebadged.

“His company makes products that are beyond well made. Doug is also a very honest person. Great products, and a great company to work with — I highly recommend them.”

Zack Farah
Owner — Gearstar Performance Transmissions

Tools

Speedometer gear calculator

Tire diameter and rear gear ratio. That's it. Bring the numbers to checkout and the kit ships with those gears in it.

Measure loaded, on the ground — not off the sidewall. Between sizes, go bigger and call us.

Your combination

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Every drive gear, same tire and ratio
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The math

20168 ÷ tire diameter × gear ratio × drive gear teeth ÷ 1001 = driven gear tooth count. For your numbers: 20168 ÷ {{ tire }} = {{ step1 }}, × {{ ratio }} = {{ step2 }}, × {{ driveTeeth }} = {{ step3 }}, ÷ 1001 = {{ drivenExact }}.

Kits that carry this
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Shop

Filter by what's actually bolted in the car.

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Nothing in the catalog matches that yet.

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This kit ships with your gear combination

Run the calculator and bring the tooth count to checkout. Yours right now: {{ comboLabel }} on a {{ tire }}" tire with {{ ratio }} gears.
Fits
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Built to order in Caddo Mills. Need it sooner than that? Call.

Cart

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Free shipping to the lower 48, no minimum. Shipping to Alaska, Hawaii or a US territory is quoted by hand — call 469-688-6985 and we'll price the freight to your address.

Checkout

Your vehicle

We cut your gears to these numbers. Get them right — the calculator fills the tooth count in for you.

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Ship to

Stripe collects the street address on the next page. The state is so an Alaska, Hawaii, or territory order can be quoted by phone instead of checked out. Orders: [email protected].

Payment

Your card is entered on Stripe's checkout page, not on this site. We never see or store the card number.

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Order
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Parts are cut to the combination above. All sales are final — see returns. Call 469-688-6985 if you want us to check the numbers first.
Southwest Fabrication

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Thanks — we're on it.

Confirmation's on its way, tracking follows when it ships.

We're cutting your gears to {{ comboLabel }}. If that's wrong, call 469-688-6985 before it goes on the machine.

Services

Resin infusion

Closed-mould vacuum infusion. Light, repeatable, and finished well enough to sit on top of a motor at a show.

01

Tooling

We pull a mould off your part, or cut the plug from scratch when there's nothing to copy.

02

Lay-up and infusion

Dry fabric laid, bagged, pulled down under vacuum, resin drawn through in one pass. No dry spots, no resin you're carrying around for nothing.

03

Finish

Trimmed, drilled, clear-coated, hardware included. Goes on the car the day it lands.

From the infusion table

Race car body panels, Corvette hoods, a carbon seat, and the Norwood race car bodywork — bagged, infused and pulled in our own shop.

Got a part in mind?

Send photos, dimensions, and how many you need. If infusion's the wrong process for it we'll tell you that instead of taking your money.

Testimonials

What customers say

If you'd like to send us feedback about your experience working with Southwest Fabrication, or about any of our products, feel free to online and let us know. We'd love to hear your thoughts.

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Worked with us? Tell us how it went.

GM tail housings

Transplanting a GM LS engine in your project and want to retain the factory speedometer and gauge cluster?

Our kit allows you to do just that. It puts a factory mechanical speedometer take-off back on a modern electronic overdrive, at the original angle, with the shifter still where the car's linkage expects it.

4L60E, 4L65E, 4L70E, 4L80E and 700R4. VSS capability stays intact, so a computer that wants a speed signal still gets one.

The problem

Electronic overdrives left the factory with no cable drive. Swap one in and the original speedometer goes dead, which usually means a full electric gauge set and a cut-up dash.

What the kit does

A machined housing with a mechanical take-off, a 40-tooth reluctor wheel and a 15-tooth drive gear. The cable threads on where it always did and the factory gauge reads true.

What you keep

Original cluster, original shifter location, original tunnel. VSS output is retained for the ECU. Nothing on the dash gives the swap away.

Fitment

Find your transmission, then order the matching kit.

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The kits

Housings and speed kits ship with gears cut to your calculated tooth count.

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Before you order

Three numbers we need.

Tire diameter, rear axle ratio and transmission model. Those three set the drive and driven tooth count, and the calculator works it out for you and carries the answer into the order.

If you are between sizes or running an odd rear gear, call the shop at 469-688-6985 and we will cut it to suit.

The tail housing itself is machined in house to accept the mechanical speedometer kit — the boss, the bore and the gear index are all cut here, not bought in.

Install guide (PDF)

Composites

Out of the shop

Parts we've laid, moulds we've cut, and cars they went on. Some of this is catalog work, some of it was one car's problem that nobody else would solve.

Got something nobody makes?

Send photos and dimensions. If we've built something close, we'll show you the part instead of describing it.

About

A small shop in East Texas that makes the parts it sells.

Southwest Fabrication started because the parts to put a modern GM driveline in an old car either didn't exist or didn't fit. So we made them — for our own cars first, then for everybody who asked.

Everything in the catalog is machined, laid up or assembled here. Nothing's drop-shipped, and when you call you get the guy who made the part, not a call center.

This page is a placeholder. Send the real history and the names and we'll set it properly.

Southwest Fabrication Made in America.
Proudly manufactured in Texas.

Tell us about the build

Year, make, engine, transmission. Tire size and gear ratio if you've got them. Photos never hurt.

Thanks — we have your message and will get back to you, usually within one business day.

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Shop

469-688-6985
[email protected]
Monday to Friday, 7am–3pm Central

Where we are

Caddo Mills, Texas
4540 FM1565, Caddo Mills, Texas 75135

Elsewhere

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Tech notes

Build write-ups and fitment guides — the stuff we end up explaining on the phone twice a week.

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All tech notes