Thanks for the extra pictures, for a VW inspired kit car it's very well designed.
As its VW based it shouldn't be too difficult to restore, there are known failure areas in respect of the floorpan but in the USA there is a big VW custom scene and a lot of original (NOS) or modified parts are parts are available.
It seems you have a complete car so it should be a hopefully straightforward restoration.
The webbing effect you mention is probably the tissue matting where the gelcoat (top 'shiny' layer) has worn away - very repairable.
There are a load of kit car sites in the US including one or two that specialise in the '60's / 70's market. I don't know the production figures for the GT 2+2 but it might be becoming rare.
It seems only 20 might have been made.
I'm assuming this would have been a fairly simple 'Remove-Beetle-body (bolted to chassis) - prepare chassis-bolt-on-fiberglass replacement.
Check this out:
http://www.ebay.com/itm/Allied-Fiber...-/181157147924