A stock 700r4 wont hold up to too much grunt, but they CAN be built. As a matter of fact, I just pulled mine out of my truck yesterday to be sent to my trans guy who does all the transmissions for mine and my friend's hotrod's around here. There's a car I helped build that runs around with with a 436 small block that makes 608 hp at the flywheel and 590 ft lbs of torque, and he's running a 700r4 with coan convertor and such. Another with a 480 hp 383 stroker with a 700r4. Planetaries are usually the first to go, and the 3rd gear clutches, but Raybestos makes a great clutch pack for these transmissions that seems to hold up nicely. How much horsepower/torque are you making? I'll beable to help you a little bit more with some more info.