[klondike98]

Looking back at the photos I have for the 84 I worked on I also had a similar layer in the bottom of mine. I believe it is probably asbestos. In my opinion you are better off just leaving it alone and putting the chassis back in over top of it when you finish restoring the chassis. Trying to take it out will cause it to break up and its the fibers that get in the air that are the problem. I usually lightly spray or coat asbestos sheets I come across with clear lacquer or a clear poly coating just to add a little stability to the sheet if its fraying but unless its falls out of the set on its own I leave it, but that's just me...of course there are a number of opinions out there so read and decide on your own.