You can use fiberglass fabric to patch the floor pan. I don't know how far gone yours is, but the pan in my truck was rusted through in the front corners and along the leading edge under the pedals. I ground it back to bright metal, then coated it with POR-15. Then I painted on fiberglass fabric over the holes with POR Patch (I think). It's been 5 years and it's still hard as rock. In my case there was no structural issue, more cosmetic plus I wanted to stop the rusting. So far, so good.
