Personally I’d just buy a set of 7 speed STI shifters new (Tourney) and keep the rest of the 600 parts on the Trek. Haven’t looked in a while but Shimano was selling brand new 7 speed STI levers at a reasonable cost. Your 600 parts should be able to handle seven speed. Just swap the freewheel or cassette. If it is Uniglide, I’d change freehub first.
Then I would sell the Cannondale complete.
I would definitely not transplant the SORA/RSX mix drivetrain with your superior 600 parts.
Last edited by wrk101; 07-19-19 at 01:16 PM.