Floorpans - Best Replacement Option?

Had an 86 Ford 5 ton Louisville series truck that I had to make a pan for, I used a retired "road construction ahead" sign, a solid 48"x48" solid sheet of aluminum. I drilled and pop riveted that in a few years ago (I still don't know anyone who can weld steel to aluminum) I then used a couple of caulk gun tubes of silicone to serve as seam sealer. This was 2+ years ago and still solid...