Would a New Floor Board fix this problem? Mine has 2-3 holes and rot/rust and didn't know if where the floor "connects to side of the cab" under the plastic trim can be fixed a new floor or not. Also, can it be done without welding?
Any help much appreciated.

 

The floor pan can be fixed, but your cab mount is missing as well. LMC truck and I think bronco graveyard as well sell replacement pieces.
You might get away with body panel adhesive and bolts, but welding is going to make a stronger repair. You're into some structural areas there.

 

Ok, in the 3rd pic does the "missing cab support box" connect to the floor there? I've got the support bracket but wasn't sure if I just need the floor pan & cab support bracket to fix this mess.