Rusty floor pan!

The only problem I would see with bonding a floor panel in is the sheet metal work required to achive a bondline that is not too thick or thin.
Aircraft bondlines are .005 -.030" anything over .030 requires a hard shim, any bondline over .060" requires stress engineering to evaluate the bond...

I would recommend buying a patch panel, fit it the best you can, and take the car to a welding shop and have the work done.
Also check out local community colleges, high schools most offer welding / body shop classes maybe they would work on the car in for a small donation.