For what it’s worth...
Not sure of your level of skill or access to skilled persons such as Rick.
I don’t know how to weld and don’t know anyone who does. And my wife certainly wouldn’t approve of spending the money to hire someone when I could learn a repair myself.
When it came time to replace parts of my M1009 floor, I bought sheet steel and got guidance from a knowledgeable person. I took measurements and cut the steel accordingly. I then made a template of sorts with cardboard and did initial shaping/bending using a ball peen hammer, with the steel in a bench vise. I followed up with laying the steel in the truck and shaping with a stiff rubber wedge and hammer until the contours were perfect. I then drilled staggered holes and used thick steel rivets to join the metal. Filled in any gaps with polyurethane caulk, primed, and then coated with bed liner. It’s held up well for a couple years, even looking good from the bottom (also sanded and coated).