Rear sway bar suggestion

I think a rear bar will help some, although the 6 leaf rear springs are going to put you pretty close to where you need to be for the rear spring rate.

If you want to really reduce the amount of body roll, you'll need to add larger torsion bars in the front. Even going up to a 1" bar will make a dramatic difference, and shouldn't compromise ride comfort much. That with the stock sway bars will be a decent street set up, especially if you're keeping 14 or 15" rims. If you're upgrading suspension items, grab a set of bilstein shocks too. The Hotchkis Fox shocks are another step up, but not necessary if you keep the torsion bars under 1.03". You could get a set of the PST torsion bars and Bilsteins from PST and get a member discount too. Do that and you should be pretty impressed with the improvement in handling. :D