600 series and larger GMC have more engine room, they fit the GMC 426, and 503 six cylinders among other engine choices. I'm not real clear on the 500 series, might be same as above.

•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-