Just buy the revo/new tmaxx stub axles and cut the threaded protion off. No drilling needed since it already has the holes.
I did this for one of my projects before.
Castle Neu 1520 on 6S LiPo Powered Gmaxx (Nitro Killer)
Predator with OS .21TM
Supermaxx with Mach .26
Revo with OS .18TZ
Kyosho ST-RR Conversion
Ofna CR with Tekin ESC/Motor (2)