From my limited experience with these cars, torque boxes, subframe connectors and a welded & reinforced K-member work wonders. Under fender braces & under radiator support significantly helps stabilize the front end. Add a custom Monte Carlo bar to finish it off and further eliminate cowl shake.

Welding up the rest of the car's unibody welds as mentioned, helps too. It all adds up, and it really helps if you start with a relatively rust free low mileage unbeaten car.

Some upgraded control arms, HD tie rods & sleeves, sway bars bigger torsion bars, stiffer springs and quality shocks will make that stiffer chassis pay off.

Beef up your driveshaft, u-joints and attachments to the rear end and transmission.

If you don't live where it freezes hard run some Nitto drag radials out back to hook it up on the street. If you plan on running common street radials, you can count on traction problems.

If you are running an automatic, spend $ on a quality torque converter matched to your combination. Better yet, put in an overdrive transmission and EFI it.