Pretty much you have two options... 126 or 130 mm between the dropouts. Doubt the frame is that old to have 120 mm rear end.

That said, if 126ish mm, you can put from 5 up to 7 cogs (or cassettes) in the bike. If you want to force the frame any wheel in 130 mm will fit any ways.

With 130 mm you can put any obviously any 130 mm rear wheel aka 8, 9 ,10 and 11 speed (campagnolo)