Hi Michael Im just going through the process now.
Gx120 has a 3/4 inch shaft so I had to change my clutch body from 5/8's (On SB Model 45) I also put a new thrust race in and drive shaft bearing. just so everything was in line and true. Drive shaft was fine on SB 45
Havent started it up yet. But its going together ok thus far.
Not sure if that helps
