It is a common misconseption that Chevrolet used year old parts for trucks as a general practice. First let me state that it is not true!!!
It is true that a few years used what appears to be passenger car sheet metal, radiator shells, etc. on the next year trucks. The first example that comes to mind is the 1928 1 ton trucks. They used a 1927 passenger style radiator shell. But, it was steel and not aluminum as the passenger. Now I am not a metalurgist or sheet metal man but I don't think you would use the same dies for aluminum and steel. The gage will likely be different. In fact the '28 1/2 ton trucks used a '28 style radiator shell but it was steel not aluminum.
Another example is the 1931 & 1932. Most feel that the front fenders are the same as 29-30 passenger. Though they are basically the same there are a few differences. I will not enumerate them here. The headlamp bar is also similar to the 29-30 but different. It has the mount pad for the horn under the headlamp where the 29-30 passenger had the horn under the hood.
Yes it is true that truck parts and passenger parts can be interchanged in a few instances with passenger parts of a year or two earlier but it definately is not the general situation.
I could go on but feel that is enough for me on this subject for now.
If you want to research an interesting subject sometime check out Sedan Deliveries. I have done quite a bit on the earliest ones.
