Just what this site needs!

[Salt Racer]

...Sounds like if everything is mechanically sound, all I'd need is 3point belts and good tires?...

Generally speaking, yes. Most OT/HPD events require 3pt. minimum belts for closed roof cars.

Before you do the baseline testing, I'd highly recommend getting good brakes and shocks. It'd be scary not being able to stop at the end of straight way, and shocks with good valving make any car much less scary doing quick lane-change type maneuvers and going through fast chicanes. I consider those two mods to be safety upgrades as much as they're performance upgrades.