Yep, here's another...this fellow put an old 250cc single-cylinder BSA engine in a Mustang...

Of course, today you could skip all of the above and simply pop for either a new 250cc P-51 California Scooter or the P-51 upgrade kit.    And if you did that, you wouldn't have to cut up a vintage Mustang motorcycle and you'd have a fully street legal, electric start, modern motorcycle!

The bike in that video above is nicely done, though.   Our compliments to the guy who engineered it!