Here is a picture of a 1946? with 6 cylinder engine. The head is in the shadows in the back. Notice the carburetor. Maybe a WCD or WGD. I'm not familiar with the detailed visual appearance of a GMC 270 and/or other GMC 6 cylinders but this would be my guess. I would go with a military gasoline engine and maybe diesel as an option.
"Adding CFM to a truck will only help at engine speeds you don't want to use." "I found there was nothing to gain beyond 400 CFM."
