What "panels" are you needing?

Volvo makes the "trestle" that the seats attach to. It spans the width of the car. If yours is just rotted a bit where is is welded to the floor, maybe you can fashion a "bridge" of metal welded to the remaining trestle and to the floor.

Trying to get at the rot under this trestle is difficult.

As for the floor area, itself, I used the side of an old washing maching!

Sure, it's flat and does not have those formed channels, but is is thick and painted already. I cut my patch about one inch larget than the hole, then used brushable seam sealer and 1/2" stainless sheet metal screws at 1-2" apart. More sealer on the seam, then rust preventative paint. Rust-paint and undercoating underneath.

If your rot is about 1" in from the pinchweld under the running board, where the drain holes are located, there is a 6" wide panel, formed to mate with the channel bends of the floors. Is has the inside mate of that pinchnweld and runs the length of the body between the wheel arches.

I got mine at:

The Yankee Trading Company
991 Bushkill Drive
Easton, PA 18042

610-559-1750

They specialize in vintage Volvo restorations
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1989 740Ti 1986 240DL 1984 244GL