From my experience the GMC trucks were generally a much heavier duty unit than the Chevy, that being the reason for the Olds engines. The GMC pickups and trucks were actually built by the Yellow Truck & Coach Company, a division of GM. Not sure when this relationship ended, I know it lasted through 1938.
I would say that a Chevy engine in a GMC would be a step backwards. The GMC's of '55-58 had Pontiac V8's with available Hydra-matic transmissions.
The 292 Chevy 6 is a very nice upgrade to the pre '54 Chevy's. Plenty of engine compartment room in lieu of trying to shoehorn a V8 into an area with limited space. With just a few modifications the 292 can be built up to 300 HP. The 292 is also adaptable to any GM automatic with no special adapters.
I generally like vehicles that are basically stock looking, however, I like them to run well, to that end I have my eyes pealed for a set of 5 lug 1930's style 15" artillery wheels, they need to be from an International. I had a '36 International 1/2 ton several years ago that had HD artillery wheels. I want the 1930's type of wheel because they will have inside clips for the hub caps.
I have an article in my collection about GMC engaging the services of Harley Earl, GM's famous car designer. GMC asked Earl to redesign their truck line to give it a more desirable appeal to the consumer. The great looking grille and 'Dual-Tone Design' of the '37-38 GMC is a sure sign of the Harley Earl touch.
