Running a feigao cool on 50-55mph is a tall order, but it could be done with a high voltage setup. Something like a 1500kv motor on 6s or 18 cells would run a fair bit cooler than a 2000kv motor on 4s or 14 cells. I would suggest you need:
MGM 120/18 or 160/18
RCM motor clamp/heatsink
5mm bore 32pitch pinions
5.5mm gold connectors (3 male, 3 female).
That should be all you need- gearing info in BrianG's signature.