[sick472]

Any chance that the rubber coating your talking about is the factory tar-like under carpet soundproofing? It's die cut from flat material about 1/10" thick and will take form to the floor pan rather nicely over time. Here is a photo of my new stuff going in. There is a piece for under the seat that is not shown in my pic. Over time this stuff could stick pretty good to the floorboards.

Depending on how far you are taking the restoration of the cab, you could leave it as it is soundproofing rather well if it is stuck down (damping vibrations). I would have to scrape it up and inspect for rust, rust removal (if neeed), lay down a heavy coat of paint, and apply the new mat.