planning on going jap engine but i need to know what's he max power i can have. been looking at toyota nissan and mazda engine (just to be different)

or any other suggestions?

i dont think there is really a "maximum" power for a car... but having said that i am sure there are certain limitations depending upon what brakes you run.. the structural integrity of the car etc etc.... engineers would know all the bits and pieces to upgrade etc..
there are plenty of beetles out there with 2.0T motors from subaru... and they would be in the 160kW range if they are stock.