As Mike said, get a handle on the condition of the frame under that metal. Pull back some of the bad spots so you can see inside the rails, if they're not so hot you may have to reassess the scope of your project. If they're okay, it's possible to make your own pans, but I don't know your skill level- I did it back in the bad old days when parts weren't available, and it was a royal PAIN. And not real pretty. Use the heaviest gauge sheetmetal that you're comfortable working with, usually 14- 18 g. depending on the part you're replacing, heavier if you can't put beads in it. Try to match to factory thickness, it'll be easier to weld up.
If you're at all in doubt- save up for the repro pans.
