For drifting I'd go with a 19T if you want to stay brushed. The thing is that you want low end torque, and a 15T will go faster and have less torque. However I've never drifted with either a 19T or 15T, so I couldn't really tell you.
For me, I started with the 27T motor (I had a Trinity C0-27 Pro stock) and it drifted pretty well with ABS. Though, it was a little too slow for me.
After I really got tired of the speed, I decided to buy a Mamba system, and picked up the 6900kV motor. The 6900kV is the equivalent of an 8 turn motor, whereas the 5700kV is the equivalent of a 10 turn. Being brushless, a lot of people use the range of 8-10.5 in terms of turns. I wish I picked up the 5700kV though, since my car seems to lack low end torque, and I really have to gear my motor down. Too much, in my opinion.
So if you stay brushed, I would go with the 19T, and pick up (if you can) the 20-25T pinions (you'll have to buy them in 20, 21 then 22,23, and 24,25 since they're in two packs) And get the 58 and 55 spur gears.
For extra mods to the car, I would definitely go with the aluminum motor mount, shaft and bearings. Other than that your car should hold up pretty well. The stock dogbones held up until I crashed into a wall with my 6900kV motor, so don't worry about snapping dogbones under the torque of a faster motor.
You can make ABS tires yourself, and 2 inch ABS is what you're looking for at a local hardware store. Or you can buy ABS tires online.
Good luck... and if you make the thing race then just switch your tires. If you were racing I would suggest getting the TRF shocks.
I am a man of few words.