Hmmm, no responses about the tranny question, eh? Well, if it helps, go to
bk-electronics and click on the motor looking thingies on the lower right corner. The BK 40 is what I'm talking about. It says it is 40mm diameter to fit all 500-800 motor sizes, weighs 86 grams, comes in ratios of 5:1, 6:1, and 7:1, and will handle 2800 watts continuously.