[AZKen]

There are no OEM parts for our trucks. People throw out that word and everybody has a different meaning. It's really not a word we should use. The Original Equipment Manufacturers are long gone. Only aftermarket parts are available new. If the part is specific for a 65 GMC 305, then it is built or rebuilt per specs. You would never want a used fuel pump and as Lizzie says, you don't want NOS parts with perishables in them. (rubber, gaskets, springs, fluids, plastic, rusted, paper)
Many times Chinese is unavoidable now-a-days. The quality of parts is impossible to know. The warranty is all you have. You can expect some parts to fail right out of the box. You just return it for another or refund and move on. A part can have just one supplier for all vendors. Once in a while, they get a bad part. Nothing they can do about it except replace.

One of the "arts" of restoration is learning how to rebuild/fix parts and how to find parts on the internet. Donor, new, NOS, rebuilt. OEM
We don't mind helping, but you should learn to "google". NAPA, Rockauto, FLAPS, Summit, Speedway Auto, Jeggs, Classic Truck Parts of America, Jim Carter, Amazon, 6066GMCCLUB "wanted". If you get stumped, we can help. I found the pump in 5 minutes, available in 3 places.