I have an 81 Trek 710, full 531 as far as I know and I love it. I converted it to a modernish 10spd drivetrain (10spd barend shifters, older XT rd, Cyclone fd, Sugino mighty tour cranks 48/34t, White Industries hubs laced to Mavic Open Pro rims and a 12-34 IRD cassette). It's a fantastic bike and will go just about anywhere

I am considering pirating the modern parts to put on my Gunnar and swapping in a combo of Superbe and 1st gen Cyclone onto my Trek