Compatible with most modern automatic and manual transmissions. Fits 1955-1957 “tri five” Fits Chevy model frames, not for use with truck frames. No welding required, bolts to frame once mounting holes are located and drilled. 1-3/4-inch round bare steel tubing with .108-inch wall thickness. 1/4-inch thick laser cut and press bent frame brackets. 3/16-inch thick crossmember end plates and transmission mounting pad. Includes hardware to mount crossmember brackets to frame and crossmember to brackets. Fits TH350, TH400, 700R4, 4L60E, and 4L80E automatic transmissions. Fits Saginaw 3/4-speed, Muncie 4-speed, and aftermarket Tremec manual transmissions. A Bolt-In Transmission Crossmember Conversion for Your Tri Five Fits Chevy Fits Chevrolet’s iconic 1955, 1956, and 1957 models, affectionately referred to by enthusiasts as a “tri-5 Fits Chevy” or “tri five Fits 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. Thankfully, we offer thousands of parts to keep your tri five Fits Chevy running and on the road no matter the build theme. The original engine and transmission fitted to the tri five Fits 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 a later small block or big block Fits Chevy engine swap it is usually a good idea to upgrade from the standard single front mount to the later side mount configuration, which allows easier accessory drive fitment, but you need to add a traditional transmission crossmember to your ’55-’57 Fits Chevy’s frame to complete the driveline support