You could use a Neu 1509/1Y motor together with a Quark Competition 80B ESC. With powerful batteries, it would be a killer setup.
If you want a Feigao, you could try a 8L but will spin really fast and get extremely hot.
Cool project! I was wondering when someone was going to do one of these.
I would say that a 9L or 10L would be a great choice of motor for that model on 4s. It would be a ton of power considering at one time I used to run an emaxx on a 9l and 4s and this will be alot lighter.
I can't decide if its more fun
to make it...
or break it...
I'm not sure that there is a 4s setup that will push a DBX to 60+ mph without gearing it to the moon and having a long run up to top speed. A 9L should put you at 50+mph on 4s though.