Depends on the level of collectibility of the bike. But generally, the originaler the better - including stuff like cable housing, bar tape, etc. The stuff that can be replaced with least damage to potential resale or the possibilty of landing that big concours trophy are wear replacement items (like bar tape, toe straps, freewheel). If you're planning on riding it, you can easily replace some of that stuff with newer stuff (especially better-functioning stuff like modern cable and housing) and save the originals for showtime. Some folks do that with things like Campagnolo globe logo brake hoods (usually by swapping out the levers rather than the hoods). Again, whether it's a high-zoot bike is a factor. The zooter, the more another collector will value originality.