keep in mind that shimano Deore was originally a touring-specific group. this was 1982, pre-MTB... these days, the modern equivalent is "MTB" stuff. 135 builds a stronger wheel, and long cage derailleurs are capable of handling larger gear ranges (bigger rear sprockets). if you have a friction shifting bike, oyu can mix and match whatever you want... I tend to use road FD, and MT RD, for example...