What is the difference in the steering gear assemblies for 3 speed column and 4 speed floor shift?
What about the differences between 1956 and 1957?
I noticed that you have a '57 GMC 3/4 ton (150), so my info is from a 55.2-60 GMC Master Parts Book and will deal strictly with '56 and '57 100, 150 and 250 series trucks. You didn't mention power steering, so I'll leave that out of the mix as well.
The case is the same and as far as I can tell so is everything inside the case.
The steering column jacket (outer tube) varies based on transmission type, 3 speed, 4 speed or Hydra-Matic. These differences are mostly (maybe all) due to holes for mounting shift linkages. The jacket and inner shaft varies in length from '56 to '57 because the '57 has a dished steering wheel and a shorter steering column. If you mount a '57 steering wheel on a '56 shaft you will find that it is about 3" closer to the driver than when mounted on a '57 shaft. The opposite is true of a '56 steering wheel on a '57 shaft.
If you have factory turn signals, the '56 turn signal stalk comes out at a 90 degree angle to the steering column while the '57 mimics the "dish angle" of the '57 steering wheel.
