Honestly, the ONLY way your going to have something that makes 400whp and drives "right" and consistently is going to be to buy a rolled '05+ STi and swap EVERYTHING. Driveline, wiring harness, dash, brakes, axles, etc.

If you try to build power in a "lesser" block, you'll spend more to make less so you might as well use the motor from the STi you're going to use for the swap.

If you try to control (engine management) your 400whp motor with anything shy of a WRX or STi harness and ecu you'll have problems, so you might as well use the harness and ecu from the STi you're going to use for the swap.

If you just put a 400whp motor in it, you'll break your tranny, so you might as well get the 6mt from the STi your going to use for the swap.

If you build your tranny you might eventually grenade a lesser diff, so you might as well use the diff from the STi you're going to use for the swap.

If you just put a 400whp motor and tranny in it, you won't be able to stop it, so you might as well use the brakes from the STi you're going to use for the swap.

If you... well, you get the point.

Siegel