Wow! Looks like you have your work cut out for you!
As for fixing all that rust, what I would do (which may or may not be "correct"), is strip it of the heavier pieces (suspension, engine, body panels, etc.), put it on jack stands, and replace the frame rails and floors. After that is done, it should be strong enough to put on a rotisserie. However, I do NOT think just doing a front tube chassis would be easier than replacing the frame rails. Not by a long shot. I would just replace them with some nice, thick, square tubing.