[BobS]

As of the 1964 GMC parts book (printed in Sep 63), the part number for that pump was 5686708. That might get you pointed in the right direction with someone who isn't afraid to break open a book instead of just punching numbers into the computer. A quick search on the internet shows it was also used on both Olds and Pontiacs so restorers of those makes might be a source of information also. So far, the only thing not leaking on mine is the pump, I suppose that day is coming.

Bob