Advice on 03 gt build

The stock motor is generally good to 400rwhp with a power adder (nitrous/supercharger/turbo charger).

If you are new to performance upgrades I wouldn’t dig in the motor first. I would first do all the basic maintenance (ex: change out brake, transmission, engine oil, and rear end fluids) and make sure everything is in great working order.

Next I would determine your long term goal for the car. If your goal is to have the power of the newer cars then look at adding a power adder early on. A low boost power adder is a blast on the stock motor.

@FertileDill You can buy a 4.6 crate motor built that will accommodate your horsepower requirements and it will be much cheaper, less headache and much less time troubleshooting, researching and trying to figure your build out. I've been there done it. I've had my motor out completely on 3 different occasions. I wish I would have pulled the motor and slapped a crate motor in with the horsepower requirements I wanted. You can go full bolt on 5k plus on parts. If your doing labor plan on spending a lot of time were talking 40+ solid hours to get 300RWH on full bolt ons. Supercharging or turbocharging your talking 5k plus to get your kit needed to push 400 horsepower and that doesn't include labor. You can find crate motors around 5k and get the power you want. Just depends on what you want to do. If your planning on painting and getting wheels done, making it a show car. I would pull the motor, have the engine bay painted when the car gets painted. I wish I'd done this with mine. I'd buy a crate motor, slam it in there after car has been redone. Take it to a tune shop and bam. Complete and you have a nice weekend warrior and show car for under 10 k. I'm including the paint job in there. That's just my two cents.