Welcome to Stovebolt.com.
GMCs were probably 1/5th-1/10th the production of same year Chevrolet trucks?
So, GMC parts that were not used across those two brands are often harder to find.
Many of the non-matching parts are engine parts, front-end/cab sheet metal, and "badging" (and, exterior colors).
Other parts up through 2-tons trucks might match.
You might to also join the oldGMCtrucks discussion board and glean information and advice from both discussion boards. There is no problem posting the same question on both boards. Some members check out both boards, and some members frequent one of the boards.
I usually go to Rockauto.com first, check-out/find the part numbers and then check NAPA, Amazon, and an Internet search on the part number. Finding a vendor with cheaper shipping and no state sales tax is another factor to consider.
The reproduction parts vendor with a good selection of GMC reproduction parts is Jim Carter Truck Parts.
