Just from what I can see, looks like the truck is peiced out of several years of trucks. The engine and most likely the chassis are GMC, '60-'62. Even then, I'm inclined to think the engine, or at least the bellhousing/clutch may be from a 2wd, as from what I understand, 4x4s didn't use the hydraulic clutch, which this truck does. The cab is definetly a '64-'66, the badge shape and location points to '65, which is at odds with the serial number.
