It is likely 128 and from that I wouldn't even consider a 126 wheel. 130 is the standard for 7,8,9 and 10 speed for both Campy and Shimano, with 11 speed Shimano at 131. I think even Campy 12sp is still 130 but not sure. That would leave almost any wheel out there as a possibility and the prices go from pretty cheap to incredibly expensive. The newer cassettes shift better even with friction shifting. I just started upgrading a 1988 or 89 C'dale and it was 128 spacing as the higher end versions of the bike with the same frame were 7 speed but the one my wife bought was 6 speed.