Lowest cost 500hp would be 351w junkyard F4TE casting. Yes I know that block is not as strong as the older block, but should be ok at that power level and roller would better with turbo because of the faster ramp rates of the roller cam.
GT40 heads “craigslist" Afr 185 if budget allows
F303 cam
42 lbs injectors “Ebay”
matching throttle body “Ebay”
Fuel pump
Fuel lines “look at the Junk yard threads”
upgraded T5
8.8 or 9 rear end “look at the Junk yard threads”
bigger radiator “look at the Junk yard threads”
Cobra break and
suspension package.
Junk yard turbo setup “theturboforums.com”
Please correct as needed. This was more or less my setup 10 years ago. I am sure I have forgot things.