I think I'm in the same situation. My newly acquired 51 has one original wheel and 3 later 15-inhers.
The problem with the newer wheels is that the pad where the clip would mount is about 1/4 inch deeper in relationship to the raised portion where the knuckle bumps are.
My quick assesment is that if you could shim the pad up 1/4 inch and get the clips in the right spot, that might work. Problem is shimming 1/4 inch, and finding the correct length rivets.
My plan of attack is to find three original wheels.
If you want to go the clip/shim rout let me know... I have a bag of clips I'll sell you cheap.
