Castle Creations motor and ESC combo recommendations for the Arrma Felony 6s (1/7th scale).

Monster X 8s w/1520-1650kv - Stock gearing (16/46) on 8s = ~65MPH
Monster X 8s w/1717-1650kv - 20 pinion/46 spur on 8s = ~75MPH

All speed estimates are with stock tire diameter, high quality batteries and appropriately sized battery connectors.
Always monitor ESC, motor and battery temperatures on new setups or when changing gearing or batteries.