I typed out a response then saw that hrrcflyer posted almost exactly what I was going to post. Ultra-Sport with fully sheeted wing, retracts and flaps, closest thing to building a warbird you will find. Not only that, but you could EASILY modify the Ultra-Sport to be a "way-standoff" Mustang. To be honest even though it would be way-standoff, it would look better than any Hanger-9 ARF. If you fully sheeted the wing, and the fuse is already fully sheeted (or slab actually), you could fiberglass and paint the plane. All great stuff if you want to practice and make mistakes on a sport model before building your true warbird.

As far as engines go, decide on one or two you are interested in and start watching the RCU and RCG classified ads. I have never paid retail for an engine. Last one I bought was a Saito 100 for $225, brand new and that was a good deal, but not the best I've come across by a long shot.