Originally Posted by KCT1986

If your old frame has 130mm spacing, and you already have a donor for 9 speed, moving over everything, except crank, should work.

A 'new' 7 speed front shifter may still have the issues with the old FD, you'll need to try and see. The 'new' front shifter may also be shorter pull as common for most in the brifter era.

The chainrings on the newer should have shift ramps & pins that the older one may not have. This will improve shifting a little.