Product Summary

Chevy LS V8, 1.75" Tube O.D., Steel, Natural

  • This LS engine mount and transmission crossmember kit is specially designed for the 1955-57 Chevy
  • Both mounts and crossmember are fully bolt in and requires no welding
  • The crossmember mount works with most modern era GM transmissions that have a mount on the tailshaft
  • Kit comes with adapter plates and polyurethane mounts for LS engines
  • Engine mount brackets locate off of factory frame rivet holes to ensure proper alignment

Comes as a Kit

Key Specs

MFG. Part #91604055
BrandSpeedway Motors

Need To Know

This Product Will Ship Free

Shipping Policies & FAQs

Quick and Easy Returns

Return Policy


  • Bolt-in LS motor mount and trans mount solution for tri five Chevy with no welding required
  • Complete kit with LS engine mounts, transmission crossmember, and hardware
  • Included mount brackets are made from 7 gauge steel and bolt to inside of frame
  • LS block adapters are laser cut from 3/8-inch thick steel
  • Polyurethane motor mounts reduce engine movement and are stronger than rubber mounts
  • Compatible with stock LS truck (Vortec) truck accessory drive
  • LS engine location provides sufficient hood clearance to use stock Vortec truck intake
  • Crossmember fits most modern automatic and manual transmission used in LS swaps
  • Crossmember made from 1-3/4-inch round steel tubing with .108-inch wall thickness
  • 1/4-inch thick welded end plates and 3/16-inch thick transmission mounting pad
  • Fits TH350, TH400, 700R4, 4L60E, and 4L80E automatic transmissions
  • Fits Saginaw 3/4-speed, Muncie 4-speed, and aftermarket Tremec manual transmissions

LS Swap Your Tri-5 Chevy Using Our Bolt-In Motor and Trans Mount Conversion Kit

Chevrolet’s iconic 1955, 1956, and 1957 models, affectionately referred to by enthusiasts as a “Tri-5 Chevy” or “tri five Chevy,” are one of the most recognizable classic cars on the planet. From usage in dozens of movies and TV shows over the decades to magazine project cars like the famed Project X (which itself was also a movie car at one time), their body lines and classic styling work well for everything from straight axle gassers to pro touring builds and everything in between.

We offer thousands of parts to keep your tri five Chevy running and on the road. Now you can repower your tri five Chevy with another iconic part of GM history, the LS engine. No doubt one of the most swapped engine platforms around the globe, powering all manner of hot rods, classics, muscle cars, trucks, and more, the LS swap is a terrific way to keep classic vehicles on the road with performance that will allow modern road speeds and the safety of keeping with today’s traffic flow. Speedway Motors’ tri five LS swap motor mount and transmission crossmember kit is the key to building your tri five LS swap with an ingenious bolt-in solution for your LS engine and transmission.

Thick Steel Motor Mount Supports and Adapters Create a Strong Mounting Solution

Knowing that the LS engine can make some significant power we put some serious thought into how to harness all that power to your tri five’s frame and minimize engine torque movement, so all your LS engine’s power makes it to the rear tires. To facilitate proper engine location for a tri five Chevy LS swap, custom frame brackets are made from heavy 7 gauge steel (that’s roughly 3/16-inch thick) that are located using factory rivet holes in your tri five Chevy’s standard seamed frame (not compatible with seamless frames).

These frame mounts are paired with LS engine block adapters made from laser cut 3/8-inch thick steel that bolt to factory mount holes on your LS block. The frame mounts and LS block adapters are shipped as bare steel, so we suggest paint or powder coating for long lasting protection and appearance. The final piece of the puzzle are our polyurethane small block chevy engine mounts. These are standard small block chevy engine mounts with interlocking safety tongue encased in tough black polyurethane insulator material. Much stronger than stock rubber small block chevy engine mounts yet dampens engine harmonics that a solid steel mount will allow to pass through to the frame and ultimately to you.

Tubular Steel Transmission Crossmember Supports Auto and Manual Transmissions

The original engine and transmission fitted to the tri five Chevy had what some would refer to as “reverse motor mounts” with two mounts straddling the side of the transmission bellhousing area and one mount at the front of the engine. When performing an LS swap to your tri 5 Chevy you not only have to convert to standard side engine mounts, but you need to add a traditional transmission crossmember to your ’55-’57 Chevy’s frame.

Our ’55-’57 Chevy transmission crossmember in this kit is specifically designed to support all the popular LS swap automatic and manual transmission options capable of being bolted up to an LS engine. Crafted from 1-3/4-inch round tubing with .108-inch wall thickness and CNC bent for precise transmission location, heavy duty 1/4-inch thick end plates are welded on along with a 3/16-inch thick transmission mount pad. 3/16-inch frame shims are included to accommodate frame variances and mounting hardware for the crossmember, and your transmission mount, (available separately) is included as well.

All You Need Are Basic Hand Tools to Add Modern LS Power To Your Tri-5 Chevy

We designed our tri five LS motor mounts and transmission crossmember for the ’55-’57 Chevy LS swap to be easy to install. The frame mount installs on the side of the frame after you grind/drill out a pair of frame rivets on each side and then use the mount as a template to drill a pair of additional holes. Once this small modification is complete everything else in our tri five LS motor mounts kit bolts together with the included hardware. There is no need to mock up engine placement, as we’ve done all the challenging work for you. Once the frame mounts are installed to the frame and the adapters and SBC motor mounts to your LS block your LS engine can be lowered into place.

Depending upon the LS engine being used you may need to update your LS with a low profile oil pan to provide enough crossmember clearance. Then you’re ready to move on with your LS swap using our bolt in transmission crossmember from the kit. Our tri five transmission crossmember for LS swaps sits atop your ’55-’57 Chevy’s frame and bolts to your LS swap transmission mount of choice. We offer both a standard rubber mount, as well as a urethane mount option. Fall in love with your tri five Chevy all over again with a modern LS swap engine and transmission.



MFG. Part #91604055
BrandSpeedway Motors
Transmission Mount IncludedNo
Tube O.D.1.75"
Material TypeSteel
Sold in QuantityKit
NotesEngine frame mounts not compatible with seamless style frame