The fastest mopars to date on road and autoX courses have had torsion bars and leaf springs. The Hotchkis Taxi, a 4 door Satellite, put down faster lap times at TireRack's test course than their usual BMW 3 series test cars with the same driver.
No reason not to run the torsion bars. Properly set up they'll perform just as well or better than a coilover conversion that will cost twice as much.
