Subframe connectors for a driver/cruiser, necessary to weld to floor?

As for torque boxes, high power manual transmission cars can certainly benefit. Any of them can, really, but Chrysler must have thought the same as big power cars with manual transmissions got torque boxes a good bit. Just look at the "whole kit" US CarTool offers for our cars. That should give you a good idea of what all you can add to strengthen these old girls up.