This is a somewhat specific question, and I haven't yet found an answer in the forums.

I am buying parts to build a touring wheelset. Instead of spending tons of money on hubs, I thought I'd put that towards rims and tires, and as people seem to really like the XT hubs for touring, I'd go for that.

I was going to get older hubs on ebay, probably, and thus have a few decades worth of parts to choose from. My question: are there notable and important differences between certain years/periods of xt / shimano touring-ish hubs? Certain good years, or years to be avoided?

Other details: Trek '83 720 frame, 100mm front (I think), 126 rear (to spread to 130). Medium weight touring, 32f 36r spoke count desired. Freehub also seems like a good idea; rim brakes.