Take a look at this thread I started a few months ago. It's mostly about early Dura Ace pads, but I've got two of the Dia Compe / Superbe pads in there as well.
Vintage brake pad refill thread
If you have the original holders, the Kool Stop Superbe pads are just about perfect. I would recommend the black over the salmon. I've had a lot of trouble with the salmon pads squealing on these Gran Compe calipers, while the black have been much quieter, and stop almost as well.