For 500hp in a third gen you really only need a TST PowermaxCR (for you with the twins program

) and a pressure box like and edge EZ or a Bully Dog Downloader. A lot of guys are running the TST and Downloader stack with good results. It would probably put you closer to 600hp, but you can use the TST adjustability to tune that

Injectors don't seem to be needed to get 600hp, but if you want more than that it looks like the injectors/CP3/fuel rail may need to be modded.
There are only a couple cams available so far. Piers, Scheid's and Don M have the only ones I know of, and I only know of a couple people running them, so there is not a lot of feedback as of yet.
As far as studs go, they are all you are going to need to hold 80+psi. Lots of guys are running twins on stock head bolts at 65+psi with few problems, so studs are just good insurance.
Sounds like it would be a fun re-power project! Hope you choose to come to the 3rd gen world!