brushless setup for xxxt II rtr???

[tonka truck]

I have just bought a losi xxxt II rtr and want to convert to brushless as less maintenance and a bit more speed (40-50kph) and runtime (9-12min). Here is my plan and setup.

I was thinking of running 6-7 cells of GP 3300 or 3700 not sure yet?? suggestions would be good. I have 3s2p 2000Mah lipo (Kokam 15c) from my RC plane that I can use - would that be enough?

I have done some research and was thinking of the novak super sport 5800?? - it is cheap and easy setup, however worried about glitching (have JR XR2i)

OR

MGM compro (not sure of amp level), but not sure of motor or gearing that would be suitable.

What would be a good bashing setup that fits the bill and is reasonably priced (AUD by the way)