914's are unibody anyway, no frame so to speak to mount the fiberglass to. Now, you can pull the engine and transmission, and most of the suspension pieces and transplant that to a VW chassis. To make it rear engine you'll need to swap the ring gear in the transmission, or modify the fiberglass to keep it mid-engine. It'll take some modding on the VW pan for a mid-engine design, but it can be done.