Today a Empi enthusiast on a Facebook Dune Buggy forum states this may be a frame built in Fresno, CA. It is likely a rare find, but unlikely to be a valuable one. In any case he suggested to install engine etc and get it street legal, clean and preserve the patina, the most unique part of it all, and enjoy where enthusiasts are. Someone just might want it very bad. If no one does, no problem, it will likely draw a good deal of interest as is. It will be an easy toy to tow to fun places to drive it.
So there, that is what I now know and this information is only a reasonable guess.