Is this your trailer?
1973 Love Bug in VA
I can't tell for sure what the wall covering is, but it could be Ensolite. Ensolite is glued on in pieces, so there are seams, and if you press with your thumb it's spongy and dense. Sound about right?
It actually looks to be in pretty good condition from the pictures, anyway. I'm curious why you're wanting to gut the interior…? It's a bigger job that many novices expect, and too often an empty shell goes on the market six months later. Best advice I've heard is to clean thoroughly, make sure the running gear (axle, tires
, lights) is in good working order, and use the trailer for at least one season before embarking on any major renovation. Of course, if you're experienced in vintage trailer rehabs, you know what you're up against…