With your jeep springs I dropped 4' in the rear, short box fleet/wood bed. Of course with your blocks you will go 7.. With Torsion bars you will not get low enough just adjusting them down to drop your rear 7'.
I put 2 1/2 drop spindles up front and used the torsion adj for another inch and it sits at the stance I want.. Not looking to go lower myself. I would say at max you might get 5' up front with drop spindles and the torsion and still have a spring rate.
To test it out jack up your front end with the wheels hanging and back off the bolt at the back of your torsion bar at the cross member (mid truck) There are two as you probably know. You will see how far you can bring it down by looking at the threads that are left up top. You must keep them somewhat tight due to needing the twist on the torsion to give you a decent spring rate. With the wheels hanging causing no tension on the suspension you should be able to release them safely.
I would suggest if you plan on going lower the cheapest way is to swop out the whole front crossmember from a later 60's if you want 6 lug or go into the 70's to get 5 lug. Then you will have spring front suspension and of course you can lower with springs,spindles etc. Do a search on crossmember swop there is tons of info on it. I might be wrong but I do not think you will be able to slam your truck with the torsion susp. If someone has they might chime in.. Some have said things like using a longer bolt in the torsion bar to help get it lower but you will be scraping the bolts on every speed bump you go over and I wouldnt want to lose the tension on my suspension while driving
Reid