I think a lot of us have done those economically indefensible but a lot of fun projects. About 1999 I bought a complete low mileage 1983 Trek 400 from a member of my bike club for $200 intending to user it as-is as a beater/errand bike. As I got it it had been modified by to original owner with Shimano 105 long reach dp brakes and Shimano 7-speed barend shifters but still had 27" wheels and a 6-speed early Shimano cassette rear hub and what was basically a BMX 46/34 crank. The owner said it didn't index very well so he was using the barends in friction mode. Well, a 6-speed cassette and 7-speed barends might explain that.

OK, so after a Frame Saver bath, the first change was to get a cheap 7-speed freewheel rear wheel and 7-speed 14x28 freewheel, still 27" but now it indexed properly. Then, I replaced the crank with an Suguino VP 52/40 and UN52 bottom bracket I already had in my parts box and, of course, it needed a new chain. Then the seatpost was replaced with a Kalloy Laprade type and an Avocet saddle both also from the parts box and a surplus Avocet 20 cyclometer. So much for "as-is".

Finally I fitted 700c wheels with a 7-speed cassette hub and 13x26 cassette, newer bars and stem, Kelly Take-Offs with 7-speed dt indexed shifters, Esge fenders, a used 105 8-speed triple crank, Shimano PD-515 clipless pedals and a few minor items.

By the time it was over I had a really decent beater but I really don't want to know how much time and money I had in it.