DIY floor pans.

Think it had something to do with clearance for catalytic convertor. Im sure someone will chime in with a solid answer.

home made panels, large flat area, i prefer 14 gauge, then 16 or 18 for the more shapely parts.
Smaller parts are easier to form.
Air hammer and various bits on a block of wood and you can shape beads and use it for forming the panels. I made my own 4 foot brake, and a planishing hammer with a frame to hold my air hammer to shape metal pieces. Its handy.