Is building a motor out of parts a good idea?

[Bash_N_Thrash]

What I want is a motor that is torquey and speedy. A good balance of the two. Most of the racing I do is with the guys at work. We make a track on the office carpet and race around. The straight is about 12' long and the rest is short turns, usually about a 3'-4' radius. I put a stage 2 red motor in mine and the guys with the stock motors are faster. The reason I put the stage 2 in was we went to a gym and raced on the basketball court and the top speed of the stock motor was not able to keep up with the stage 2 blue or yellow. So now I want to swap back to the stock motor or even better yet, build a motor that is a good balance for all types of racing.

I have lots of parts to use at my disposal. I have a SB Pro, stock Xmods motor, a PN ball bearing can, a Z-130-A-BB from Mini-Z racer and 4 Stage 2 motors. In doing some reading (alot of reading) it sounds like just adding the SBP magnets to the Stage 2 motor with the 11 tooth pinion would be a good fix. My idea was to put the Stage 2 (11T) armature in the PN ball bearing can with the SBP magnets. I know the pinions are a pain to pull so I might not do the ball bearing end bell and just use the can itself with the Stage 2 armature.

The only other idea I had was to put a Xmods pinion on my Z-130-AA-BB motor and drop that in. Not sure about how it would work with the esc in the Xmods but it was safe with the Mini-Z one.
Any opinions or suggestions?