the calmini torsion bars are something like 30% stiffer than stock. over time stock torsion bars will start to sag and even more so once you crank them up to achieve lift with the new upper arms. when i was still IFS i ran the stock torsion bars with upper control arms and had no issues. actually it rode very well and wasn't too harsh. however, if and when you add a steel front bumper, winch, etc....you will likely need some stronger torsion bars.
regarding the body lift...i had a 3" body lift and the suspension lift. i was running 33s at the time and had installed a rear locker and the truck did great. had nice road manners and would go just about anywhere i wanted to take it. with the body lift...just go back from time to time and torque the bolts. especially right after its installed. it'll keep things right and reduce any squeaking, etc. i know most folks don't like body lifts, but i have never had an issue with mine in the 8 years its been installed.
hope that helped. later.