Gearing help

Hi,

Could anyone give me pointers on how to increase the gear ratio beyond what the smallest available motor pinion permits? I'm looking to convert an Ofna buggy and would really like to try get 15:1 final ratio. Apparently one can install a larger spur gear or use smaller bevel gears in the front and rear diffs. However, I can't find any specific information about what size spur and bevel gears are available that will fit Ofna diffs.

Can anyone offer me some pointers please?


Thanks,
Aragon