Hes using mod 1 pinons and revo spurs I believe.
The only problem with using a neu (or any other larger diameter motor can) with the smaller revo spurs is going to be gearing it low enough. I would switch over to 32p Jato spurs if you dont already have too much invested in mod 1 pinions, you can get those a little bigger. I adapted a 44t mod1 RS4 single speed spur to the traxxas slipper without too much hassle, that could help as well. Ive also heard that there are bigger MGT spurs that can fit the traxxas slipper.