Here's the advice I got from TCI(not Total Cost Involved but from Torque Converters Incorperated). A properly built 350 will take 450 HP, same built 400 will take 600 HP, anything more and it takes a powerglide since they have been run in 5000 HP fuelers and survived. He also stressed that the torque is more of a facter than the HP and that the stall rating on a stall converter means nothing if on a low torque engine.
