I used to run T-bars in my pick-up with a total chaos like long A-arm suspension. Actually it was one of the original long A-arm suspension that Total chaos later copied and improved.
The drawbacks with torsion bars are (I believe) not being able to make a progressive suspension set up and the weakness in the set up is where the torsion bar mounts to the A-arms. The entire weight of the front of the truck rest on this mount, which has a longitude load on a laterial mount. The problem with early aftermarket tubular A-arms like mine is that the mounts would develope cracks and eventually snap in two.
I had this happen on my kit and it left me stranded at the end of a trail. I was able to limp back to a main road with the suspension resting on bumpstops, fender removed and the upper A-arm attached before the remaining suspension disintigrated.
Other than that fiasco, I didn't have any problems with my torsion bar set up and it did make other aspects of the suspension like the steering easier to set up.
I imagine the coil spring A-arms are much easier to develope with the way the loads are set up. Even though TC is an expert at torsion bar A-arms, designing ones for the excessive loads of a 100, with as much as 7000-8000lbs gross weight is probably more than they want to deal with. Also, the torsion bar mount is on the lower A-arm, which might makes thing more complicated. And finally, the major advantage of the torsion bar A-arms is that they are extended several inches, which improves travel by increasing the outer arc with minimal impact on the inner arc, but this also greatly affects the load on the outer CV and on a full time 4WD, this is not an easy thing to overcome. Especially for as few units as they would end up selling.
unk03: . I assume TC has a successful business model but the decision to invest aftermarket lift suspension components on a brand new model year...and one that starts at $65k...seems strange at best. Never mind they have ignored the now 10-year old 100 series market altogether.
