Coil overs is not the only answer for making a truck perform ok ...
We RACE on torsion bars, and frankly haul ass through the whoops.
One key is, you can never have too much shock.
If I were to be setting up a prerunner (which I am) with torsion bars, I'd run the "1" sport trac (heaviest) bars, a shock hoop with at least a 2.5" remote reservior shock. A lot of making any truck work well is spending the time and money to get the rearend to work well too ....
The only major downside to the torsions is you will have to replace them. We can get a set to go about 500 miles of HARD use before they are sagged and wasted. We also do not start with hardly any "twist". Our arms, once everything is settled, are close to level.