Help me wrap my head around these for a bit.

Not the top of the line stuff, I'm trying to fit something into the 38(t) kit. I worked on some kit track links and I think they'll hold up fine, it'll just be a tedious job to drill out 5 holes on each by hand (the slightest use of speed will distort the horns). For giggles, I hooked up Tamiya's dual motor gearbox for their 1/35 series to a RX-18. It worked great, but at 7+ volts, i doubt those little motors would last even if they were strong enough to move this kit.

Promaxx makes a 180 that runs on 7.2, which would be a good option and Tamiya makes a bunch of project gearboxes in all different gear ratios.

You guys mention ratios in the 3:1 and 4:1 range as being the target. And as I understand it, thats reducing the motor speed for more torque and manageable output. Promaxx makes gearboxes in the same ratio but it's for props and it's only one large gear off the pinion.

Any suggestions on what to look for smaller (plastic okay, probably preffered) gearboxes that could take a motor compatible with RX-18 output?