Your asking about the 4 piston 65-72 disc brakes?
If your looking to mail order parts, Rock Auto is good.
NAPA can get kits, or any of your local parts stores that carries, or can get, Raybestos parts.
Rockauto is always good plus someone can give you a 5% discount code. I just ordered mine from calipersonline.com $110 each but they have stainless pistons. Rockauto had 3 or 4 differant ones to choose from i think starting around $60 if i remember correctly.
oops just got off work misread your post. I have some seals for them id sell pretty cheap if you need them. they are from partsmaster. Like posted above napa probley has everything you need, but kinda expensive at times