You're generally on point Marv, drifting is not about speed at all, it is about exhibition of skill while the car is "seemingly" out of control. I digress I would recommend a 15T brushed motor such as the stock Sprint 2 Firebolt, good balance of high speed and torque. Lock the rear diff, leave the front open or get a 1 way front diff. Don't lock the front unless you want a lot of understeer and horrible response. With the rear locked you will have loads of stability and you will be able to initiate your slide at top speed and anywhere below, with the open rear you will not be able to reach high speed drifts and with the front locked you won't either.