Not too sure about the Wurlitzers, but the AD trucks 1/2, 3/4 and 1 ton frames were all different underneath the box. 1/2 had a big kick up, 3/4 a little one (I think) and the 1 tons had no kick up at all.
Bed sides for the trucks were the same from 40-53 (different lengths of course). I read that in a book called Chevrolet Trucks by John Gunnell. The mounting holes were in different spots for the fenders. but if you couldn’t find 41-46 box sides the later ones could be used if the holes were filled and redrilled.
