Well, the RZ is a formidable car in any right. In a number of 150,000cr challenges, it has held it's own against the Viper and the Vette Z06. In a few OLR sessions, it has performed equal and in some case better than the Vette and the Viper.
Yes, it can easily handle the Amateur American Championship. THe key to remember when running amateur, is the AI cheat. Yes, in a bg way. They'll always remain within a few seconds of your time, unless you take a Bazooka to it.
So stay smooth, don't over power the car, and keep the racing clean. Once you're out in front, make even lines, and don't push the car more than you have to.
T4 tires should last about 5 laps. If the race is longer, just go with T3 or T2 tires. They'll give you the best grip. Try to time the cold-warm-hot-burnt cycle to match the length of the race. At the end of the race, you should be on orange tires.
I used a moderately modified Camaro SS for that series. My Seattle Curse held strong and I needed three attempts at the Reverse track.
Good luck,
AO