D8 gearing

Hi which pinion and spur should i get for my D8?
neu motor 1512 1.5d +mmmv3 on maxamps 6500 2x7.4v
i want to get kyosho spur to.
should i change the motor or should i go 3s or keep the 4s setup?not to get to hot in 20 minutes run.
i got rcm motor mount fro lightning stadium pro to it.
need the gearing help here.for all around indor and outdoor.
Thanks