Larry, I managed to do a bit of research on your question but had to postpone replying until my better 1/2 and I got dinner out of the way. Anyhow, a search of 3 of my Chevy Master Parts books (1929-46, 1929-53 and 1929-57) provided some results to help answer your questions.
Your "Axle pivot" is known as "Seat - Cap - Plate, Rear Spring", Parts Group 5.403 in the parts books. There is a "Seal - Bolt, Rear Spring Seat" (rubber 1-7/8" OD x 1 I.D. x 3/16 thick) GM# 597267 listed in all 3 books under Group 5.404, but the application lists show that was only used on 1938-54 Passenger Cars and 1947-54 1/2 ton Trucks. No reference to being used on your 1937 GC. I have attached some screen shots below from 2 of the books to help show what I found. Hope this is helpful.
