Bicycle frame updating
Additional information is on Sheldon Brown's Seatpost Size Database.
A 1982 730 and a 1983 720 have been reported using a stem size of 0.833" (21.15mm); a 22.2 stem was too big.
To join the new group one must obtain a Google Groups account and then apply for membership into the Classic Rendezvous Lightweight Vintage group.
Most members of these lists get enjoyment out of placing an unneeded part with a good home; the monetary return is secondary.
Seatpost Diameter - Nearly all road Treks prior to the mid 90s have the standard seatpost diameter of 27.2mm.
Exceptions are Models TX200 and TX300, which have a diameter of 26.8mm, and the Model 170 at 27.4mm.
Additionally, a 1985 Model 2000 (aluminum bonded frame) with a 27.4mm seatpost has been reported.