I would save the P-51 for a third plane and get some experience on a mid wing sport plane first like a Sig Mid Star or somthing similar.

Most P-51's tend to nose over on landing if you are not very careful or unless you put the main landing gear farther forward than usual.

My P-51 (Midwest 40 size) was about the 5th plane I built. I flew it a lot, I put bomb drop mechanisms on it, but looking back I don't think it was any more fun to fly than my other sport planes.

Good luck with whatever you do, and follow whatever dreams you have.