i would like to know if the clutch, fly wheel or transmission had any modifications since the 2003

no,i dont think so.

2003 had 2 sizes in the flywheel but they dropped 1 size halfway through production, and continued with that

Actually they changed there clutches after the 03 model since they had the premature failure problems with the 03. The clutches on the Tiburon's are pretty much as reliable as a piece of cardboard. The 04+ are just a beefier piece of carboard but they are still alot better then the 03's. I own a 2003 tiburon gt v6 and i still got the stock clutch at 86,000 miles. so i got lucky.

in august of 2003 the flywheel was changed a couple thousanths of an inch in the base. when replaceing the flyweel in an 03 the flywheel has to be physically measured to make sure it will fit, and also you have to ask whoever your ordering it from to measure it for you. its a pain in the rectum