I am planning on modifying the stock arms, and thought of doing it while they are still on the beams, that way I don't mess with the caster at all, making sure that I chock all the tires so the truck doesn't move, taking many measurements before cutting the arms, and taking even more measurements during the fabrication.
As far as mounting, was kinda thinking of moving the drop brackets for the arms back about 6-8", getting some angled steel, boxed steel, or a tube with flat steel at the ends to weld or bolt to the brackets, and welding on the mounts for the heim joints at the end of the arms onto that, about 3" inside the rails to help get rid of/lessen the rub that I already have with those 33's.
I had also already thought of the F250 tower mod a while ago when I first started the build. $30 at the Flagstaff U-Pick-It yard gets me two towers and two F250 shocks. Currently (and I just measured it) I have a 11" cycle but only a 3.5" drop from resting length with the shocks I have now...no idea what they were originally for (thinking it was for the D**** Ram that's sitting without a rear axle), but they fit the 5" lift and the Ex itself, providing that I swapped out the bushings on the eye at the bottom of the shock.
Would I be better off doing the F250 conversion for the time being and waiting to do the radius arms just for now, or should I just wait and do the whole thing in one shot? I know that I'll actually be better off doing both...I have some time to think about it...