750 into an X2:
From the 750:
Engine
Intake / Carb
E-box
Maybe Throttle cable ?
From the 650:
Everything else (Bedplate, Mounts, Driveshaft, S/S switch, Exhaust manifold / pipe, etc...)
650 into an XI:
No idea, I would guess if you take the 650 E-box and coil, Engine, use 750 exhaust mani /...