Well from what I've seen I'll list the different options available:

1 - Non smoke n sound (rx13)1 or 2 speed forwards and backwards. All plastic tracks and gearboxes
2 - Smoke n sound (rx14 or rx18) 10 speed forwards and backwards. All plastic tracks and gearboxes unless specified as metal.

As far as I'm aware none come with the 3:1 boxes installed but some places do install the normal metal boxes, tracks and sprockets for you but at a much higher cost. I also assume its the same for the infra red series as the airsoft.