I was doing speed runs with the rustler (same transmission) geared 19/54 with a Velineon. You should probably go with a Jato 32p spur (which will fit fine on your slash slipper clutch). Then go with a 17-19 tooth 5mm 32p pinion depending on whether you want 42 or 46 mph.
I run Mod 1 gearing in my VXL ruster using a Revo 40 tooth spur and a RCM 16 tooth pinion I prefer it over the 32 pitch
Mod1 or 32p work fine. You may not be able to get the cover back on with either, but it does not matter with the larger gear teeth. I run a 58t spur with an 18t pinion in one pede and it does fine. Jota or revo spurs work fine, and you can mod mgt spurs to work too (gives you more choices in mod1)