The only difference in the front fenders is the presence of a hole for the parking light. I have a GMC front fender on each of my '49 and '52 trucks. I just welded the holes shut. One could drill a hole in a Chevrolet fender for their GMC parking light.
You won't need to move the steering box if you use exhaust manifolds from a '55 265 cubic inch V8. They are very narrow and dump downward toward the front of the engine.
You definitely don't want a rack and pinion for a straight axle. Too much going on to make it safe to drive.

1952 5-window - return to "as built" condition | 1950 3100 with a 235 and a T-5 transmission