Back then, Chevy & GMC were two completely different trucks.
Even the frame on a GMC was heavier gauge steel than a Chevy.
I've heard that many times, but have been unable to find a GM document that confirms it, and those frames I've measured are not different.
As an example, a 1-ton '50 Chevy and a 1-ton '54 GMC both have a frame made from 7/32nds material. Its the same guage.
I know this because I own both and have carefully measured them. They are the same.
While its possible there are differences in the lighter trucks I did a measurement comparison on 1/2-ton trucks once and concluded there was no difference. I don't have the numbers in my head though.
The claim may originate in an improper comparison. Chevrolet's biggest truck at the time was a 2-ton. GMC made larger trucks with the same cab design. Its likely a GMC 3- or 3-1/2 ton truck has a thicker frame rail than a 2-ton Chevy or GMC.
In a recent discussion about fenders someone else pointed out that the fenders used on both Chevy and GMC 1/2-, 3/4- and 1-ton trucks '47 to '53 have the same GM part number. It would be interesting to see how many parts that is true of.
There are many differences between the two and some are obvious such as grills, hoods and motors, but some of the differences people talk about I've never seen substantiated and the evidence does not seem to support it.
