I see what you mean. If my wallet would allow it, I'd already have an expo with a 5.0 waiting for it's heart to be transplanted into my Ranger.
I'd say that any coil sprung part can be replaced with the torsion bar suspension equivalent. Bear in mind that you also have the hubs and knuckles to deal with as a coil sprung 2wd is very different than one with a torsion bar setup, even if the truck is a 2wd. With the coil sprung Ranger, the hub and rotor are one piece. In a torsion bar setup, the rotor is separate from the hub. I believe the calipers, pads, and caliper brackets are the same, though. That being said I believe the front axel, too, is different as a result of this. The power steering rack and pump as well as tirerods and all that should be the same across torsion bar and coil sprung rangers, although there's a chance of them being different.
See what I mean when I say there's a lot different? Lol. Mostly it's in the front, I believe. I don't know of anything in the rear end that's different between coil and torsion rangers.
Another thing. sway bars, end links and control arms may also be different, too, as a result of the hubs and possibly knuckles being different. Although I don't know if the explorer parts will bolt on or not. They should but I can't promise.