Hey puffdogg, if you need to buy the batterys make shure you go for 40/80C + (steady/peak). Look for quality it will pay off.
Capacity should be 6000mAh + giving you runntimes of 10 minutes and more depending on the track.
With lower C rates the batteries will get hot and tend to puff.
Pinion I would use is 19T +/- 1T delivering a top speed of 80 km/h and good acceleration.
Thats a good choice running on a medium size track.