Thanks for the help. I *do* have a set of 650a wheels that I can use for measuring. Since I have no other parts for the bicycle at the moment -- it's a frame, fork & headset, I'll be free to purchase components that will fit. I could possibly even go the hub brake route, but I was not planning to.

700c would not be the end of the world, but I do like the look of 650b wheels. There is a lot more tire choice if I stick with 700c though. Decisions, decisions. I need to strip the frame and get it powdercoated first. DH says "No, just build it." But I already have a Retrovelo and a nearly reassembled 70s Sports so there is no rush. Might as well make this into a lovely bicycle.