Great Planes has a couple of good conversion charts on their ElectriFly website:

http://www.electrifly.com/powersyste...brushless.html

http://www.electrifly.com/powersyste...brushless.html

You have to take a few of their recommendations with a grain of salt. With recommendations for speed controllers, for example, Great Planes doesn't offer an ESC in 18A or 20A, so their recommendations jump straight from 12A to 25A. They give you the Diameter/Length/kV rating info of their recommended part for motors, however, so you can use their charts to shop for whichever brand you prefer.