I was about to reply to your first post but you pretty much answered your own questions here. You've got it figured out.
EDIT - Alternatively you could do a 3" body lift. I'd prefer a suspension lift if it were my truck but I know there are several people here running body lifts that like them.
Also I never clarified but yes cranking the bars will increase spring rate and ride quality will suffer.
Also, if indeed the torsion bar crank does affect the spring rate, does that mean if I go with RCX and leave totally uncranked for a 4" lift my front end is going to be under-sprung so to speak?
I don't want 5" of suspension travel when I hit a speed bump.