A Cobri Rotating case mount from http://www.e-flightline.com/
would probably fit and you can get a huge range of ratios to play with. Figure out what is the biggest diameter prop which will fit the aircraft... then look at gear ratios which will get that prop spinning at ~75% of Kv x V.
The HK suggestions for maximum power are well over-the-top... that 87g motor is probably good for 3W/g = 260W... so if you want to draw 28A on 3s you are probably just okay.
Badcock doesn't have thrust data for 13x10 but here's 13x8: http://www.badcock.net/cgi-bin/power...+++0&Temp=20.0
That seems to be plenty of thrust (60oz!)... and by computing Kv x V x .75 to get your prop speed of 6500rpm from 2700Kv and 10.5v (3s).. you would need about 3.25:1 gearbox ratio.
Certainly you could use a heli motor... they are essentially the same, but typically higher Kv.