I can't comment on the BA/BF, but for FG falcons, the XR6 and XT are essentially the same other than cosmetics. The engines are the same, the gearboxes are the same. With the FG, if you went to the turbo version later, the gearbox and wiring will be different.
A stock FG motor would be fine for a clubman style car. Plenty of power and cheap.