If you are going for a Mamba Max you might as well do the job properly and have a look at a Holmes Hobbies
Crawlmaster brushless.
If you are going to use the Mamba in something else as well then use it, but if you don't need the extra performance most crawlers are moving over to the Sidewinder. It's half the price, easier to fit in the chassis and there's absolutely no performance difference between them in a crawler.
If you aren't planning on running brushless then I would recommend a Tekin FX-R instead. Smoother, can be programmed in the field and an amazing drag brake, and lots of crawlers are moving away from the CC ESCs to the FX-R.
http://www.rccrawler.com/forum/showthread.php?t=105316
For brushed motors the Axial ratios seem to be designed around a 55 turn motor, so you have a choice of them from Integy, Reedy, Novak, etc. I use Integy motors, much cheaper than the other makes which is a consideration when you have two of them in each truck. Go to higher winds for more torque, lower for more speed.