One other thing, if you go to 700c rims you'll probably need to cold set your frame so that it has rear dropout spacing to match a modern road hub (130mm). That's also going to mean a lot of changes to your drivetrain. That is, unless you can find a 700c wheelset with a hub to match the existing spacing on your frame. Or you could always build your own wheels, or have them built, using a hub to match your frame's dropout spacing and whatever 700c rims you choose. Problems, problems.....