The beginners setup to going fast in an S197 Boss 302.
Swap to 18x11 wheels with 315 tires. Alternatively, 19x11 on 305 tires.
Change the rear brakes to the GT500 rotors and caliper extension bracket.
Change the rear ratio to 3.55:1. If you've got a non-Boss GT, use 3.31:1 ratio and change the differential to a T2R.
Add rear lower arm relocation brackets, and optionally, lower adjustable arms.
Add camber plates (should be done with the tires).
Add an adjustable panhard bar or Watts link (also should be done with the tires).
At a minimum use the Bilsteins and lowering springs, consider swapping the springs to 450# front with a sleeve kit and 175# rear using Vorshlag parts.
Swap to the heavier, adjustable, Whiteline sway bars, particularly in the rear.
Consider deleting the oil heater in favor of an air-to-oil oil cooler.
Add a stiffer bushing to the transmission to help with miss-shifts. Either the Whiteline bushing reinforcement or the Energy Suspension shifter bushing, or both.
Add track worthy brake pads and brake cooling.
Those changes will get you -VERY- far into the performance of the S197.
A better seat and harness to hold you in place would be my next addition. Actually you can add the harness to the stock seat, but a racing style seat works better. The harness will require a rollbar, and the best I've used is the Maximum Motorsport part.
Next I'd address the front arm bushings. The Whiteline KCA433 kit duplicates the racing arm bushings.
Beyond that, better dampers, effective aero, engine tuning and bolt-ons for power, and even bigger tires are on the list.