I don't see a problem using modern material in restoring a vintage unit, but make sure the "newer" material has the same structural ability as the older one. As far as the insulation is concerned you will be hard pressed to find something as versatile as the new generation fiberglass to give you the R-value per inch, flexible installation...it won't fracture or crack when flexed, as well as ease of installation. Another factor to consider is that a lot of the foam insulations lose R-value as they age, as well as the chemical off gassing. As far as the floors are concerned I don't know of anything that would work better than plywood, unless you wanted to use an aluminum planking. Most of the wood composite boards on the market are not as structurally stable as a good grade of plywood, same goes for the plastic resin composites. Ever seen on of those after it has been laying in the sun unsupported? Just a few thoughts....
Aaron
