The newer Novak motors also have a 5mm shaft. And please, don't go with a Velineon motor.
This is what you need:
http://www.rc-monster.com/proddetail...nion5mm&cat=40
SH Z-Car, Custom Crawler, 8s Savage,
12s XTM XLB 1/7 buggy,
4wd 4-link rear/IFS Pro4 truck,
Custom Hyper 10 Short Course,
Belt-Drive Mammoth ST 1/8 truggy, 4s 17.5 MM Pro HPI Blitz