There was no rear support in 54/55-st for the 1/2 ton truck transmission (unless you had a HydraMatic transmission). The motor mounts and the frame crossbrace for the motor mounts changed in 1954, supposedly making the rear mount for the 3-sp and 4-sp transmission unnecessary.
I have never had one on my 1/2-ton '54 pickup and it had a 4-sp on it from the factory (no holes in the steering column for the 3-sp shifter box).
Tim
