Its 6 speed I need. I have a 7 currently fitted on an early Hyperglide freehub body (the one with internal and external threading for both types of lock ring) but I still have the M730 6 speed SIS shifters which i am using on friction mode as they wont work on the seven cassette. There is a difference of around 0.35mm on the spacers between the cogs on 6 and 7 speed cassettes and it means poor shifting when in SIS mode, hence the need for a 6 speed cassette.
I've been up to my ancient LBS and come away with two bins full of cassette spares, hopefully there are spacers of the correct width in there somewhere. I have a new 28-12 to canibalise for the cogs. If I cannot find spacers I will fire up the lathe and machine some from scratch. The things we do eh?
Thanks for you help guys.
Cheers
Si