I know were all speculating here, and its fun to do, that's why we're doing it!

but I do plan on finding the owner and having a chat and getting some facts.
I do however, personally believe its a Pantah motor - smaller displacement as well.
I've owned a few Ducati's since 1998. In fact my first Ducati was a Monster of that year. I've also, up until recently owned a 748R (2000 model). The motors' on these machines are definitely a generation or two ahead of the motor I saw on that car.
If you look at the fin design on the cylinder heads, its looks like the type of motor found on Pantah's...
?
Dale