kinda bringing this topic back from the dead but I recently stuck a very cheap 1600Kv 6-pole outrunner in my Revo 3.3 conversion.

geared 15/36 with Elektri-Clutch. it pulls about 70A from a full-throttle start on 6s. Tops out at almost 40mph, but handles extremely well because it's lightweight (9lbs).
I used that motor cause it's roughly the same size as a standard 540, and will fit in the 36mm Tekno mount I had laying around. For larger outrunner experiments (or if I had the 42mm mount) I was looking at the
Castle Vertigo motors that were $40, but the only ones left now are really low 220Kv. Kind of hard to gear those properly as you'd only get 30mph geared 30/36 (RCM sells a 30t 1.0M pinion!) on 12s lipo lol.