Well, with everyone posting Bruder conversions I thought that I'd throw mine in here. I took a different route and went with regular gear motors for the tracks.
The shafts on the motors aren't long enought to get through the track housing so i extended it with some couplings.
Turns out that the center of the drive sproket after checking it with drill bits is 4mm so I drilled through and fastened a hub to the outside of the sproket with screws and it worked fine.
Hooked a Saber tooth to the motors and It was moving quite well. Next up is the cylinders.
Thanks for looking.
Rob