mbx5t vs a baja 5b?

I am building a mbx5t and had a set-up of racing, with the Neu 1515 1y, 4s pack and the MM. My LHS closed down there track ,and the closest track to me is about 80 miles away. So racing is out of my head right now.
Now How would it be possible for this BL mugen beat a baja? The guy has put a 5.5 HP engine in it, and this other stuff he wont tell me..My thought is it might to 60, if not higher? i have no clue. I saw on RCM that there is a flightpower 6s pack for $300
Would the 1515 1y on 6s work? I want this thing to hit 70+ if possible. I would like the highest quality batteries. I know NEU and castle creations is high quality already, should i go with polyquest or flightpower? the polyquest is 20C constent and 30C max, the flightpower is around 30C constant and 50C max. Would this mean more power? We are going to be drag racing, and it will be long so i need speed and i also need it so this is a reliable system. Also could i tame the 6s power? On the speed control could i set it up so it acts like its on 4s or is that out of the question? I wont want it controlable but i would like pure speed. What do you guys think?