I use a kokam 3200 mah 20c (64 amp) pack. The main thing is that you make sure the max continuous amp rate is above 45 amps, assuming your running 3s lipo and 9 turn 380 motor. You need at least a 60 amp 2s pack for a 6 turn 380. How much runtime are you looking for?
Check out my custom converted 8ight:
Sub 7lb, lowest CG of any 1/8 buggy