I think you should build the Monza and give me the Mustang.... When can I come pick it up????

Both cars would be a fun build, me being a Ford guy I would have to go with the Mustang, but that's just me.

Whicever of the two you decide to build they are of course both unibodies and would benefit significantly from frame ties and maybe even a 6 point roll bar to stiffen the car up.