power selection for a 2WD Slash can be tricky... for dirt oval and straight line drag racing (with reasonable traction), I'm more inclined to think you might appreciate having more power, but there comes a point where having too much power can cause your car to do wheelies or worse, spin out of control in a tight turn. I suppose that's where proper adjustment of the slipper comes into play, but not having an oil sealed diff will make it more difficult to get optimal power transfer when accelerating hard on corner exit.

Do you guys prep your concrete floor by spraying with grape soda to increase traction?

Reason I ask is that the more traction you get, the more power you can reasonably apply. Another trick to consider is getting 17mm hex adapters and invest in quality GT8 wheels from Sweep. That will give you far more of an advantage than anything else, especially if you sauce your tires just before each race

I would keep your Castle motor for now, that should be plenty of power, if anything it may be too much, ha!

If anyone else in your group is running a 4WD car, then running your 2WD against them is like taking a knife into a gun fight.