There was one I believe called "Stiletto", I think it raced in the 80's. It's alot like the Galloping Ghost, ie tall tail, race canopy, and clipped wings. The other one I can think of off the top of my head is "Precious Metal". Again it is an air racing mustang so certain aspects are very similar to the previous two. I believe it runs two counter rotating propellors for a total of 6 blades. The plane is known for the shiny props they run and in my humble opinion some really hideous green wings.
As for custom models there was a guy who worked at a hobby store down here in Orlando who built a complete range of P-51s in 1/18 scale. Most of which were mods of 21st century and bbi stuff. He also did a couple air racers including the Stiletto.
If you have some time on your hands this website has quite a few pictures of racing Mustangs both original condition and modded. The Stiletto and Precious Metal are in near the bottom of the page.
http://www.mustangsmustangs.com/p-51/p5 ... cers.shtml
Hope you enjoy it