on our cars our rods are powder coated they aren't strong internals at all. so our car is rated to handle no more than 450 rwhp in the motor and on the auto tranny. what happens if you exceed this you might get away with it for a little bit depending on your driving habits, but what happens a lot is that you will end up throwing number 7 out your motor. from all the research i have done that is the most common.
if you want your car to be a lot faster i would recommend 4.10 gears, a 3000 stall, one piece drive shaft, full bolt ons, cams, and I'm running a 75 shot and am really happy with it. but get a really good tune i am running bama tunes and haven't had any problems but a dyno tune is the way to go especially with nitrous
but if you still want a power-adder the only way to make our cars have any serious power is to get a better block and forge the internals, upgrade the tranny level 10 and tci are most popular, you will need a one piece drive shaft, you can get away with the rear end but if you want to make 600 plus at the wheels i would recommend a 9" rear but it depends on how you drive and how hard your car will hook