I don't know all the details on swapping a GMC to a Chevy frame, but I think there is an issue with how the radiator support mounts.
I am sure it can be made to work, but you may want to start asking about how to do it.
Could be the radiator support from the Chevy fits the GMC?

Grigg


1951 GMC 250 in the Project Journals
1948 Chevrolet 6400 - Detroit Diesel 4-53T - Roadranger 10 speed overdrive - 4 wheel disc brakes
1952 Chevrolet 3800 pickup
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"First, get a clear notion of what you desire to accomplish, and then in all probability you will succeed in doing it..." -Henry Maudslay-