+1 on the notion of whatever puts your butt in the saddle ... and, whatever gets you excited about wrenching on the bikes you have, and gets you interested in the next project. I'd just add that anything which actually alters the real old stuff is problematic. Case in point: as I've mentioned here before, I'm restoring a 1972 Bob Jackson with a decidedly non-period Shimano arabesque group. It's not TOO far off, it looks cool, and it works real well, not to mention the fact that lots of Brit lightweights were sold as frames only back then so componentry was up to the buyer anyway. That being said, if I ever want to go period correct, the Shimano can come off, 1972 Campy can go on, and nobody will be the wiser.