I'm rebuilding a vintage Fuji and have assembled an almost everything I need in components in Suntour Superbe (period correct for the bike) but I know that finding a Superbe freewheel is going to be darn near impossible. I would like to replace the current freewheel (worn out) with something modern but of comparable quality etc. I do not want to go to a cassette as they weren't even around when the bike was new. Any suggestions?