small ball joint vs big small joint

I just picked up a set of upper control arms on ebay. When I opened them up they looked the same as my uppers I pulled off my 64. I didn't do any serious measuring yet but they look like the same that came off my 9 inch drums. I guess what I was hoping for is that my eyes are failing and that I didn't get bad info from the seller. He said they came off a 75 disk brake a body. Is the difference between the big and small ball joints significant? I will press the old joints out tomorrow but I thought maybe I could get a quick answer