To the teams that have been doing FIRST for a while: the drill gearboxes from 2000-2002 are a perfect fit for the RS775 motors - the mounting holes match exactly and you get to choose between a 20:1 or 64:1 reduction - you can even change gears, if you forget the pain it was to do that back in the day!
The only modification needed is for the pinion: you either buy (remember PIC?), manufacture (EDM, most likely) or steal one. We went ungracious on the drill and took the 12 (?) teeth, 0.7 metric module pinion from an old one we had around. The drill motor shaft is 4 mm and the RS775' is 5 mm. The pinion is hardened, so we had to anneal it (real quick with a blow torch) in order to machine. May seem a lot of work, but it really took us about two hours from concept to fully-functioning product.