Shifter cable pull x mech ratio = sprocket spacing.

you can either play the game of mixing and matching shifters and mechs to achieve (or not) the sprocket spacing you have or vice versea, match your sprockets to your gears. Sometimes youll get lucky, like 10s Campag shifters with Shimano mechs indexing perfectly on Shimano 8 speed sprockets, other times it’ll be close but not quite and you might need to either adjust sprocket spacing or pull ratios to get what you want.

there are many setups that will work, and equally many that won’t, get your calculator out and start playing!

i have several bikes with CampagTourNo* setups working perfectly, no skips no jumps no chattering, but they did need custom sprocket spacing...

* Campag 10speed ergo with Suntour Vx mech and Shimano 8 speed cassette with custom spacers.