You need to try just one more set of brifters (well, ergos really). Campy 8 speed indexes perfectly with Shimano 7 speed cassettes (and I assume your freewheel as well). The left shifter also has 7 clicks, so you have plenty of travel, and can trim to avoid chain rub.

I happen to have a spare set of used 8 speed Veloce (I think) not in use...