As someone else mentioned, I'm a big fan of the KMC X8.93 chain for 6,7,8 speeds. I've used it on 7-speed Suntour and Shimano cogs without problem. Have not tried Campy but I'd expect it to work.

Bought it on Amazon for $11.57 and it comes with the KMC Missing Link. For that price, there's just no reason to mess around with stubborn links on an old chain.

KMC X8.93 Chain 7.1mm 6-7-8 speed