Stock fresh C heads, stock forged crank from a Cobra, billet rods and probe pistons.
You'll also need to completely overhaul the suspension, chassis, fuel, driveline etc...
What are you trying to do with this car? What are your goals? Have you ever had a 4 figure HP car before much less 500 or 600?
Looking at about $20k for a well done 1000hp built car and that's if everything goes to plan.
2000 Mustang GT Steeda #0048 34k miles. 99 Cobra 4V swapped, FTBR IRS swapped, exhaust, tuned by James Gordon.
Just because I give you advice, doesn't mean I know more than you. Its just means I've done more stupid ****.