Found this on the rotaworx web site about the TA51
Quote:
450+rwkw - Do you want to win dyno competitions? Do you want to smoke your tyres at 200kph? Then you can't go past one these babies, definitely not for the faint hearted and not recommended for street use!
I read that as saying "Lag Monster".
Go for the other turbine housing, sounds closer to an acceptable size.
Have you read the thread on 1JZ piston speed, Might give you more RPM to play with.