Tko600

My guess, at around 500rwhp, you'll be putting down somewhere over 600ftlb of torque. I hope you're also planning an aftermarket block for that kind of horsepower, the stock 302 won't cut it. How well your gearbox handles the torque is largely up to you. I have a turbo 302 putting down ~400hp / 500 ft. lbs and am still using the stock t5. I don't run slicks and I don't dump the clutch, so I haven't had any issues after many, many runs.

I also wouldn't use the term "slapping a turbo kit on it." You'll find there's a LOT more to it than that, that 500 hp is a fairly high goal for a streetable car, and it's going to get very expensive the further you go above ~450hp. So you might rethink what you want, and focus on what you need (considering your goals for the car and your budget).