The gauges in my 49 GMC 100 are nearly identical to the gauges in my 49 Chevy 3100. OIl press = 0-30, ammeter and gas level. The difference is in engine temp where the Chevy goes to 212 and the GMC goes to 220.. Other than horn button and the script identifying the manufacturer the interiors are also nearly identical.
re. swapping the front clip. There would be more involved to put a GMC from clip on a Chevy than just bolt on as the front clip-to-cross member attachment is different. You can see the differences in the pics posted above of the differences. It can be done but it would be alot of cutting and welding work.
IMHO the GMC with it's slightly extended engine bay clearance is better suited to later model engine upgrades, if that's what one wants to do.
It's not unusual to find Chevy engines in GMC body's.
Without the engine numbers its hard to say but I'll swag someone dropped a 216/235 engine in a GMC.
