If both the GMC and Chevy are regular pickup trucks the doors and hood will interchange. The stainless mouldings (around the glass) on the doors are different between Chevys and GMCs, assuming there is any on either truck.
The hoods also interchange from 1960-66, you just need to have the latch that goes with the hood. There are two styles, the 60-61 hood has a downward facing latch accessed in the gap between the hood and the radiator support. On the 62-66 the release handle is pointing toward the driver side accessible through the rectangular opening in the front of the hood.
