I think it would be awesome to have a '66 Mustang with a body that could be either a fastback, coupe, or convertible along with the parts for a six or eight (or perhaps just stock/custom eight), auto and manual transmission, and a few wheel choices. It would cost a bundle but would certainly be worth it due to the different build options. Plus it is a well known and popular subject.
Edit: with what Mark mentioned, it would probably be better off in 1/12 scale.