In my opinion that frame would be a mistake for three reasons. First, it is a racing frame and has little clearance for fenders on rando-optimal tires like 700Cx32's. Second, you cannot upgrade to a modern drivetrain because it has over-the-bottom-bracket cable routing and therefore over-the-rear-chainstay cable routing. If you try to spread the rear triangle and put in a modern wheel with something like an 11/32 cassette, you'll find that the chain rubs on the derailleur cable in the smaller cogs. I have an '82 Trek 614 that has the over-BB cable routing that I had planned to upgrade to modern gearing but then found out the problems above so I used it for commuting until I gave it to my son. Third, there are decent modern-design frames to be had at prices not much above that Trek, e.g. the Soma Grand Randonneur--someone was trying to sell a used one on EBay recently for about $180 and you can get new ones for $400. If you don't want 650B then there are probably plenty of decent TIG-welded steel frames available that are suited for randonneuring and that don't have lots of question marks associated with them like any third-of-a-century-old frame; e.g. Soma Smoothie, of which there are several on the Bay between $200 and $400.

That said, I have an '84 Trek 610 that I liked very much for randonneuring. I have an '82 Trek 728 that has touring geometry but regular 531 tubeset. It's OK for randonneuring but the long rear chainstays make the frame overly flexy. Both these bikes are now in commuter service since I bought a Soma Grand Randonneur for randonneuring use. I also have an '85 Trek 500 built up as a fixie--totally useless for randonneuring because you can't fit tires much bigger than 23's with fenders. My wife has an '86 Trek 400 that is well-suited to randonneuring, particularly since I converted it to 650B.

Following are some comments on early-model Treks. But prices on the old Trek frames seem to be higher than they were several years ago--I'd probably just get a new frame.

AVOID '81 Trek 610/613/614 and '82 Trek 613/614 because the Ishiwata CCL fork crown does not have a proper lug point so it is a failure vector.

R531=Reynolds 531=R531
NCO=Reynolds New Continental Oval fork

Low-Trail, high-quality
Except as noted, all have 73 degree head angle, 55mm rake = 43mm trail with 650Bx42 tires.

1976 TX700=R531+NCO
1977 TX700=R531+NCO
1978 710=R531+NCO, 910=Columbus SL/SP+NCO
1979 710=R531+NCO, 910=Columbus SL/SP+NCO
1980 710=R531+NCO, 910=Columbus SL/SP
1981 AVOID 610/613/614, see above
1982 AVOID 613/614, see above
1983 600/620/630/640 = R531C + mangalloy fork -- rear-rack + water-bottle cage

1984 610=R531CS frame+fork; has 52mm rake=49.6mm trail with 650Bx42 tires.

1982 720/728=R531, 72 degree head+52 mm rake==> 52mm trail with 650Bx42 tires.

Low-Trail Treks from
SF Cyclotouring: About Low Trail, and Low Trail Treks