Okay, a Power 60 motor (400kv) on 5s2p A123, or better yet 4s lipo (lower top speed) should be just about right for a maxx or Revo truck.
Top speed would be around 48mph with 5s2p A123, or 45mph on 4s lipo.
OR, on the extreme torque end... the Power 110 (295kv) on 5s lipo or 6s2p A123 for a little over 45mph, and crazy, crazy torque... that would be a silent, deadly machine.