[sidewaysalfa]

As someone who has time trialed street cars for over 20 years here is my suggestion.
Don't worry about tearing out insulation, carpet, etc. If you are good enough a driver that 30 lbs of weight makes a difference then . . . . . And driving a gutted car long distances is quite fatiguing, I know.
Put in a roll bar, not a cage. That way you can get at the back seat to store stuff and still have some chassis stifness and safety.
Buy the best race seat you can that will also work for your Monday - Friday use.
Use a clip in 5 or 6 point harness so that you can use the stock belts also.
Tear the suspension completely apart and upgrade or replace as much rubber stuff as you can.
Same with the brake system.
Drain every fluid and replace them.
Put an exhaust system that is not too loud for long trips to the track.
You are looking for reliable, not race car. Try to get to every nut and bolt on the car sometime before you get to the track.
And put in a decent radio/cd player and a couple of good speakers. It helps on long drives to the track.
Remember you are looking for reliable. There is nothing worse for me to see a student missing out on Driving School while they are fixing something that should have been done the week before.
Good luck, and keep the rubber side down.
And if you are ever in So Calif when we have a Driver's School, sign up and stop by.