A Neu motor would be my choice, but a Feigao C XL is the next best thing. You can't beat the price/performance ratio.

and gearing, i will use the kyosho plastic spur from the rc monster store that is 46 tooth i think, im thinking a 15t pinion. what would you guys recomend

Kinda confused here...How many cells? 9XL correct?

9xl will be the motor and i will be running 16 cells. two 8 cell packs.
in the future when i get more money i will invest in a nice lehner or neu motor.

gearing?

I would get a 14 and a 15T pinion.

thx
recap:
mamba max esc
feigao 9xl
kyosho plastic spur 47 teeth'
pinion: steel 15t
2 8cell ni mh packs
5mm thick aluminum for motor mount

anything else i am forgetting?

One thing. A UBEC.

...will the pinion reach the spur with a 5mm mount? Or is the amount of shaft protuding from the 9XL quite a lot?

Is the motormount part of the diff-holder or is the motormount a 'stand allone' type of mount? normally; with nice pinion (read beefy) you got the ability to have the pinion for 3/5th on the shaft and still be fine. In theory, the further the actual gear sits from the motor, the faster the bearing on the side of the pinion will wear out.

The 15 tooth sounds like a good strating point. 16 cells on a 9xl should be nice.
I would try to make a motor mount and diff holder together less chance of
flex between them.