I have a 1978 Trek with bar end friction shifters. Currently it has a 6 speed rear gears (threaded cluster). I have another wheel which can accept 8, 9, or 10 speed cassettes and was thinking that as long as the limit screws on the derailleur would back out to cover the gears I could pretty easily put an 8 speed cassette on (this other wheel) and place it in the bike. I'm thinking that all I would need to swap out was the wheel with the larger capacity cassette and the chain (spread the stays also to accept the 130mm width) so unless someone thinks I'm wrong here, my question here is this; does anyone know how large a cassette this Shimano 600 derailleur could handle? It looks like while they kept the model name of the derailleur, they modified it every few years and I don't know how to properly date it other than to assume it came on the bike which is a 1978 vintage Trek.
Also assuming I swap out the chain, again, I'm thinking that I would only have to possibibly re adjust the front derailleur to work with this new thinner chain???? I hope I hope I hope.....