The GMC and Chevy cabs are the same as long as you are conparing same year cabs (except for the dash and maybe a few brackets).
The 1955 cab is a one year cab.
The 56-57 are the same.
The 58-59 are the same.
The difference in the 3 cabs is the shape of the fender flair, so a 56 fender won't fit right on a 55 or 58 cab.
Doors are the same for all Chevy's 55-2 thru 59.
GMC's could have 2 different doors for the LCF's, smooth or with the fender extension bump.
I should have mentioned the GMC cabs with the smooth doors will have different fender flairs then the Chevy/GMC's with the Fender extension.
Mike B
