I've thought about doing his over a race chassis with Challenger panels. It can be done for a few grand worth of replacement panels. However, in my case I wouldn't' t need the inner structure to hang interior from and I wouldn't be concerned with how tight and weather proof it would all be. Adding the inner structures would likely double the cost (unless you have a donor for all/most of these) and complexity and then you have the challenge of melding of the donor chassis to the new body structure and adjusting for those differences in alignment to create a solid appearance.

Possible, sure, easy, not at all. There are a number of these out there. Do a deep dive into google to find them. I think even the Hot Rod Magazine archives may have a few.