I just buy the same gear than my radio is. By the way, look at www.servocity.com
They show the Futaba servos, size, Torque, weight, and speed. I think 9151s would be what you are looking for, but they have not got metal gears. Also, look for what the Futaba sponsered guys at the TOC were using in their set-ups. If you look, you can probably find a site that has their set-ups.
Hope this helps.
Robert.