Floor Pan Rust Problems and Question got an Idea?

As I type all of this the car is sitting in the garage, up on ramps. After reading a lot of posts here and asking some questions that had been asked before (its hard for a new person to search the postings because they dont have the vocabulary for the car yet) I went down to check the passenger side floorboard and the floor support.

You guessed it, rust. Big time. There really is no support rail and it is rusted right up to the Torsion Rod mounting point on the frame. Dug in and figured out what had happened. The floor is super solid on the inside. The PO put in a new floor, above the old one! Its a fabbed floor, but a darn good fit and solid as a rock, just not stock and no drain holes, stamping etc. He eaither bent it himself or had someone else do it.

I dont know what to do about it yet. Cut out BOTH floors? Cut out the rusted section of the original floor and order a replacement floor pan and support cut the pan to fit the bad section weld it in and then weld the floor support and the front piece up to the suspension mount? Maybe cut out the original floor pan and then add the floor support and then do the next piece up to the suspension point.

I dont know yet, ordered a air nibbler to help with the cut out portion to cut back to good metal on the original pan to see what I have.

Any ideas? What would you do?