I used HS81s on diced carrot, and converted to metal gears, using the metal gear kit, sussex models used to stock it, not cheap though.
You can use the metal setup even though the final drive isnt 360, as if you look through the other gears youll find a thinner one that matches the final drive, the smaller gear that is fixed to this fits inside the nylon part of the final drive, and bobs yer uncle... works best if you are doing a speed mod at the same time, or youll need 4 gear kits!!
That reads really badly, give me a bell if you are interested, and Ill try and dig out a photo...
What it might be worth saying is that after a couple of lon fights this set up burnt out the motors on diced carrot (modelworld 2002?), I reckoned after it was a lot of bother, and used another motor set.

pics of sweet little DC here: http://dangerousvegetables.tripod.com/dc/dc.htmhttp://dangerousvegetables.tripod.com/dc/dc.htm