We wanted to build it up for years or reliable use as cheaply but solidly as possible. This wasn't going to be a gravel 'mutt' or a 'parts-bin' bike or whatever (although you might call it both), it was going to be her bike that we both hoped would serve her as well as my beloved 720. In the end we did use many parts that I had laying around, spending just an additional $175 out of pocket including the $95 shifters. If I were to try to charge her for the inter-familial parts-swapping a la Dayton's failed tax plan maybe the total actual value investment would have been closer to $450.
The stock wheel size was 27". We were able to swap to 700c wheels without any modifications whatsoever with the adjustment given by the brakes. I also swapped to modern pad holders and pads just to improve braking/ease.
The bars that came on the bike were seriously, seriously long reach and got swapped right away (along with the too-long for her stem).
Stock seatpost/saddle were insanely heavy and were swapped for more adjustability.
Entire drivetrain was swapped to modern 10 speed. I had to 'cold-set' the rear spacing to 130, but now all of my, dozens?, or road wheelsets are useable on this bike.
The whole package worked out pretty well. Only real 'issue' currently is that there is no way with the modern 10 speed brake/shifters (microshift branded) and the vintage brakes to 'open' the brakes for wheel removal. With the 700x30 tires on it currently you can only install or remove the wheels with a flatted tire. This could be solved in the future in a variety of ways, or just let be.
51cm Trek 400 frame/fork
stock brakeset with upgraded pads/holders
700c bontrager SSR wheelset
700x30 Challenge Almanzo tires
PZ Racing compact crankset
microshift 10 speed shifters/brake levers
shimano 6600 cassette (12-25)
wtb speed she saddle
vintage ITM stem
3T short reach/drop ergo bars
We've been out on a couple or rides already totalling about 40 miles. She seems very happy with it both on pavement and off.