I don't know anything about the gearing on trucks and I know that the general rule of thumb is to lock the truck into second gear when converting. Since I built the MGT for my 8 year old son, I didn't want it to be too fast. I locked it into first gear, am running the 49T spur with a 16T pinion on the 8XL with a 4S lipo pack. The only thing I accomplished was to make it a beast. It goes over anything, wheelies on demand (even at a good clip) AND it's still pretty fast. I'd guesstimate around 30 mph.