Personally I would stay away from anything with 50c you should be ok with a 30c cont. A cust of Kurt@URCHobby has a Backdraft that he converted to run asphalt racing, he runs a 40c lipo and has gone thru 3 or 4 motors at $60 a pop but it is nastyon the course he says... I would just run a 20c 25c const witha30-35 burst and be done if that won't work for you then get this:

http://www.castlecreations.com/produ...a_monster.html

my buddy had in his HPI Savage Flux truck ($600 new )and he could run6s on it.. and it laughed at it....................... it would eat 4s for breakfast and crap 6s..... dead reliable ............it was sick fast !!!! but that system alonewould cost about as much as a new Backdraft 8e.