The June 1971 Trucks Parts Listing has the 4434 (stamped) GM part number 6415726.
Attached is a picture of a factory rebuilt pump 24434.
In 1979 the pump is stamped 40217 and GM continues using the same part number.
Attached is a picture of a NOS 40217.
The pump looks different, has a top that's crimped on and the base is thicker and requires longer screws.
These pumps are now HISTORY and a smart person would look for good original pumps to have for back-up.
Don't depend on FLAPS and online stores which now carry new reproduction pumps from Asia.

Just because a pump is rebuilt or NOS doesn't mean the pump is fit for modern Ethanol gasoline.
It's up to you to find out before you buy.
Attachments
24434.jpg (42.48 KB, 45 downloads)
40217.jpg (59.06 KB, 45 downloads)

"Adding CFM to a truck will only help at engine speeds you don't want to use."
"I found there was nothing to gain beyond 400 CFM."