Your going to be VERY tire limited with 225/60/15's. Tire choice in that size is pretty much limited to hockey pucks. That doesn't mean you can't improve things a lot vs stock though.
As for the set up-
1.03" torsion bars- normally I'd say larger, but with 225's your tires won't keep up with stiffer bars anyway. Use Moog 7103 offset bushings for the stock UCA's to get to the alignment numbers you'll want. Hellwig makes nice sway bars, I use the tubular front 1 1/8” bar, #55905. The solid rear 3/4” A-body bar is #6907. ( I use a 7/8" E body rear sway bar, but again, this would be way too much for 225's). For rear springs, you can use Mopar Performance Oval Track Leaf Springs #P4529414 (or P4529415 for +1", but the zero arch 15's would be better). I think you'd still need 1” bushings for the rear spring eye, those are Energy suspension 2-2117G. I used AFCO's on my Duster, but the part # I used is no longer available and they're pretty much identical to the P4529414's. For shocks the RCD Bilsteins would be fine. The Hotchkis Fox shocks are better for larger torsion bars like the 1.12's I run, but with 1.03's and those tires I think the RCD's would be more than up to the task.
The alignment #'s that Steve posted are right on, normally you want as much + caster as you can get but with manual steering anything more than +3 to +4 will be a pain to turn.
If you did all of that your car would definitely handle a lot better than stock, but it'll come down to tires if you want it to do any better. A Duster can fit A LOT of tire, even in fairly stock form. 275's will fit in the back with no modifications at all. In the front the best you'll do with 15" rims is a 235 (unless you modify the fenders), and even that will be tight on the fenders. If you go to 17" rims you can run up to a 255 in the front without any issues. 18's allow for a 275 in the front. I run 275/35/18's in the front and 295/35/18's out back, but I have a 1/2" spring offset and I trimmed the quarter lips in the back.
Handling really comes down to tires. The Hotchkis Challenger pulls .95g on the skidpad. Last I heard it was running 275/35/18's in the front and 295/40/18's in the back, with Falken Azenis RT-615's.
