I know the rear motor mount for the 55 - 59 V8 cars are different than the same year of truck. I would think the I6 mounts are also different, but I can't locate any parts in a quick search.

I V8 and I6 truck bell housing bolts from the bottom of the crossmember with a single 1/2 bolt on each side, whereas the pass, car V8 has two smaller bolts each side that bolt into the crossmember in the horizontal possition. I am not sure about the car I6.

54 Chevy build pics.