Torque boxes and frame connectors. When are they required?

sbh126 said
Well, the title pretty much sums it up. I'm about to drop in my 500 HP (Hopefully) 440 and I hadn't thought about beefing up the frame. When is it required? If I get frame connectors do I still need torque boxes? Who makes a decent set of these. Preferably a bolt in set. I'd also rather not cut the floor.
Also I was running the slant 6 driveshaft with my mild 318. Is it ok to keep using this as long as I get a loop for it? Brewers has the U joints to make it work. I'm just not sure if it will hold up. Any advise is greatly appreciated.

All factory big blocks had torque boxes, that will tell you something. Had my 67 fixed up with Auto Rust Technicians welded torque boxes and frame connectors. I did not have to cut the floor. Big block cars used the large universal joint. I'd go that route and get it ballanced by someone who really knows what they are doing.