1. Tires.
Forget those Coopers. They are a cheap tire with matching cheap performance.
With a good 'brand' tire like Goodyears/Michelin, traction will be improved greatly.

2. Brakes. Currently stock drums, manual.
I've heard about improved drumbrake linings but this will mostly put more heat into the already inadequate drums.
I would at least look into fabbing ducting to direct/route fresh air onto each wheel/brake.
Brake-fade might put a quick end to the fun after just a couple of rounds.

3. Suspension. Stock torsion and new OEM rear leaf springs.
- So far, just a slightly stiffer front sway to reduce oversteer. He's found a front sway he likes from Hotchkis (I like the FirmFeel front & rears on my '65. We each have our druthers).

4. Shocks. No idea what he has now, but definitely plain street spec.
Bilstein, QA1, Hotchkis/Fox all make good shocks which will be a league above the 'cheaper' stuff out there.
Adjustable shocks would preferred. This will also greatly improve regular driving and are easy to install.

5. Seating. Stock bench seat.
How about securely fabbing/mounting a temporary sheet of rubber to improve grip on the seat.