I agree, I run 125 on a h/c/i 302, I had 125 on my stock motor, but I wanted to step it up to 175. If you had a wet kit I wouldnt hesitate to run 250.
There is only so much nitrous a stock headed/cam/intake motor can take and still be useful. He is going to reach the point where one shot well net him close to the same amount of power as the next shot up without upgrading the h/c/i. Kind of like the law of deminishing returns