Daniel wrote: "I have never found a very useful way to patch the casing so that the tube didn't eventually pinch through and re-puncture."
I've used shoe goo in the past, the stuff for repairing running shoes. Just don't use too much or you go buhbumping down the road. It works really well for gluing down cuts in casings.
I found a few NOS Clement Paris Roubaix tires, I know there not Seta Silks but were they any good? worth $15. each?