Originally Posted by Fibonachu
I am doing a firewall mounted, power brake conversion on my 58 and as a side effect I have a bunch of spare/unneeded holes in the floor (old MC fill, brake light switch mounts, pedal hole, etc) that I want to fill.

I could weld them shut, but I don't want to do too permanent of a "fix" in case someone eventually wants to out this cab back to stock.

I am thinking about getting some of that foil backed butyl rubber mat and covering the whole floor as a sound/heat barrier. It is self-adhesive, so it would stick over the holes and seal them against moisture/dirt intrusion.

Any better suggestions?
That is exactly what I do to "cover" extra holes. I do that because it is in the same vein as what the factory did with all of the unused factory holes on these trucks. They used an asphalt looking material on the inside.

1952 5-window - return to "as built" condition | 1950 3100 with a 235 and a T-5 transmission