Oh dear LM, after all that work.......Sinco, you are correct
. It is the Javelin V6 STOL, now referred to as the Ford V6 STOL and nicknamed the Defunky Cub!
The engine was of course a Ford V6, and as I discovered, if you do a search for that and Piper PA-22 you'll come up with the reference to the Javelin. I'll forward the details by separate message.
In the meantime, its over to you Sinco.