Campag and Shimano 7 are both the same cog spacing, so getting bits is not a problem, and at least you can mix and match. 7 speed freewheels are also relatively easy to find.
There are plenty of spares available for Campag hubs, and they are easily rebuildable. I'd just get my LBS to build the wheels up.
If you ever want to upgrade your drivetrain to more speeds, then go ahead and get the rear respaced to 130mm (you are probably 126mm at present so it's no big deal.)
For now I'd just rebuild the wheels, but service and check the hubs over carefully first (dismantly, clean, replace bearings, check for worn races)
Ride it or milk it!