I would go atleast 60A continous to make life easy on the batteries. I just built a TS2 electric on a lower from Fullers. Check out these threads.
[link=http://www.rcuniverse.com/forum/m_6072870/tm.htm]Brushless Top Speed 2[/link]
[link=http://www.offshoreelectrics.com/forums/showthread.php?t=853]More Detailed Build[/link]