Did a rebuild on mine last summer...
If you google it, can find a several folks that rebuilt them. Also a very good video on doing a rebuild on a Caddy, or something else.
I bought the "kit" from Napa, cost about 18 bucks, but came with a box of 10 rubber kits in it...so have nine spares... (Napa 660-1000, believe was listed as kit for 54 chevy truck, no Kaiser's in my Napa store computer for these.......)
Prying it apart was worst part, .......no peening over the tabs once work hardened was worse....be careful!
Looked at several alternative/new valves, but none were "better" than going back with stock job. Do make sure you get the proper action on the cable, for off/on. as I recall it pushes (extends at valve) to shut off, and pulls (gets shorter) to turn on.... check it? Do know that many I found in catalogs/computer, worked the other way from one in my Manhattan...
found the link to repair guy, has pictures, not video....:
http://www.pbase.com/czechman/rancoBob L.