first go read all of the tech pages, every single one of them, then go back and read them again, they will answer most of you questions
first you must do the suspention,
a stock style 10.8 disk brake setup is mandatory no matter what your goal is, mpbrakes can help you there, or you can spend a month trying to get the part together off of ebay
add a bigger set of torsion bars, how big is depending on what you want to do, .990 are about the lowest you can go with a bigblock to handle well, 1.14 will make it handle the best but you will feel every like crack in the road, so a smaller down to .990 for more ride comfort,
also you must have poly bushings, give it a firmer feel
good shocks at a 4 corners
but the thing that makes the biggest difference is tires, its about 50% of how well you can handle, notice jim's car has 4 slicks

if you want to keep it the sleeper look you, unfortunately, shouldnt go much over a stock tire size but go on tirerack.com and search around, a sticky tire makes all of the diference
this is all i have gotten to on my project so far but these mods make all of the difference
this page does a small sum up of everything:
http://www.bigblockdart.com/techpages/tips.shtmlfeel free to ask anything you want but try and do a quick search first using the search function because most stuff has already been wentover