NJ-GT

No track and no autocross requires full lock, or anything closer to full lock.

For parking lot maneuvers, McDonalds trips, cars and coffee parking, stick to skinny street tires.

Carrera GT

Right. There is a "race circuit" spec.

I ran 265 and 345 in 19's in R's and A's at the race circuit spec, so you'll have no problem. I ran maybe 2.2 or 2.4 front camber, you'll maybe get the front inside shoulder scuffing the plastic of the lower edge behind the front bumper, and some rubbing the rears, but nothing I found worrisome and not in every set, so there's some variability, I think the A's can run a more squared shoulder and rub a bit.

It's a tricky compromise to get the ride height without going to a heavier spring --- the 3.8 RS rewards lower ride height, so it's worth it. It's really transformative, I'd say worth two full seconds at Thunderhill where a good time is 2:00 flat for me and lowered to get the rear suspension "right" ... even a scrappy time trial lap was high :57's and the only improvement in the car was the ride height.

If you don't bring down the ride height going to stickier rubber, you'll have to be conscious of driving especially smoothly to load the springs and sways. Don't just stiffen the sways to artificially induce low speed spring. You'll find the Hoosiers are characterized by initially skate, which becomes a very enjoyable and fast way to drive a 911. There are other tricks there you can pick up in the paddock.

The 345 in the rear creates a lot of traction (max attack on the wing, too, with lowered ride height) so expect the car to have a fairly sharp peak at traction limit -- this won't confusticate the SC/TC, you won't get any intervention until you make a mistake, but it will give you some "moments" if you're not feeling it, if you have the tires a bit off their best temp or you're on a track that isn't conducive to high thresholds.

I would consider 315's on the rear next time and make the car probably just as quick on most tracks, but less fearsome at high speeds.