im looking at getting another mustang as i have been out of the game for 6 yrs i intend on building and engine and adding a blower within a yr of purchasing the car i dont really care about irs because in the 99-01 cobras it seems like more of a head ache then its worth. so my question is there anything that makes a it worsth spending the extra money on a 99-01 cobra compared to a 99-04 gt i know it has 4 valve heads but im looking to build to 500-550hp and i no that is more than doable on a 2v. and i can save a large chunk of money towards building the bottom end on a gt over the cobra

 

Sounds to me like you'd be best off with a GT and apply the price difference vs 99/01 Cobra toward your build. Obviously the Cobra is a better starting point, but would still need forged internals like a GT for your power goals. I'm not sure what the differences in the IRS are between the 99/01 and 03/04 Cobra but it seems reasonable to think it can be beefed up the same as an 03/04, or if you plan on hitting the track a lot then swapped out for SRA.