....... I have a 7sp Trek from 1993 and often feel it needs more gears,
........ You may have to coldset the rear stays from 140mm to 145mm OLD to fit in a 8sp+ rear hub.
......
Our T50 was 3x7 28-44-54 x 12-30; now 3x9 26-44-54 x 11-34.
There are three no coldest options that I am aware of:
1. narrow a Shimano HF-08 from 145 to 140mm - easy there is a 5mm spacer on the NDS; take it out, re-center the axle on the hub.
2. Wheelmaster hubs with spacing washers - this is what I did, works great.
http://www.amazon.com/Wheel-Master-A...-6&keywords=40
http://www.amazon.com/Wheel-Master-T...-5&keywords=40
combined with Wheelsmith spokes and Velocity Dyad rims; SRAM cassette, SRAM X.9 RD, SRAM X.0 twist grip (flat bar tandem). They have a 14mm axle with sealed bearings.
3. DT Swiss TD 540 135mm hub with spacing washers - DT used to offer 140mm hubs, but no longer listed on their website, by do show up on eBay from time to time - expensive.