HELP! 02' GT wanting 500HP

You can't run an air-to-air IC with a positive displacement blower (ie KB).

IMO it makes no sense to try to source a rare Cobra mill when there are a plethora of blower-ready shortblocks from any number of reputable aftermarket sources.

And +1 with what Nightfire said: Intercooled KBs put the charge cooler directly under the blower discharge port, in the manifold between the cylinder banks. You simply can't package an air-to-air setup with this arrangement. It's an air-to-water setup with the heat exchanger for the coolant placed in front of the A/C condenser behind the grille with a separate pump to move the coolant between the charge cooler in the manifold and the heat exchanger up front.

Assuming you have a stout shortblock and you have the blower on the motor ready to go, you're going to need a pretty good fuel system and you're going to want some chassis stiffening, suspension and tires to make it all worthwhile and safe.

There are many ways to get there but it's a package deal. As others are telling you, it's far more than the just rebuilding the engine. Fuel, chassis, brakes, suspension, all have to be addressed. Mine runs 500HP on 91 octane fuel and could probably hit 700+ at the rear with good fuel.

550 rwhp is an arbitrary goal. What several of the people are alluding to is set more than just HP goals. There are several components to get there and limitations to the 2V mustang. 'safe' conservative cut offs for HP limits (up to debate and depend on form of FI)
Engine Internals ~400rwhp
3650 transmission (assuming you have a manual) ~500rwhp
Clutch - just sloths away quicker depending on combo of power/driving style/miles
Fuel injectors - Stock ones are 19lbs- ~290-300rwhp
Stock Fuel pump- 300rwhp

Considering several of these factors the best bang/buck for HP is a supercharger kit like a vortech or kenne bell which offers the fuel injectors/tuning software/fuel pump or boost-a-pump. With intercooling you can have 400rwhp and still maintain near stock driveability - you might want to think about your goals and what your budget will allow. Once you go above 400rwhp you need to start thinking about engine/drivetrain improvements and big money.

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