Ive got a SBC 350, around 520 hp range and will be adding 250 shot of N20. This thursday and friday a friend and I will be tearing into a TH350 supposedly rebuilt not long ago, my plan is a full manual reverse valve body, shift kit and kevlar clutches. My question is, can i run a lockup stall and not be worried about shattering a input shaft? Ive always heard its a down fall but ive heard alot about the new style converters and it seems that may be a thing of the past? Will there be a significant gain? who would you recommend?

Some more info ive got the comp cam 270H cam and it requires a 2000+ stall and ill be running hoosier slicks.