Exhaust

From what I can tell the Basic Hedman Headers Part#68300 Will work just fine but theres a few things you should consider.

1.) These headers do not have the the ports for smog injection.

2.) Some modifications may have to be made to retain the stock Catalytic Converters.

3.) These will not fit with the steering damper inside the front crossmember.

Those are just a few things to consider. Due to Notation 1 and 2 these headers definetely wont work in California if the vehicle needs to be smogged Bi-Annually. Id say they are pretty good headers and its just a matter if they will fit and how much work you want do to make them fit.

On another note your mufflers are going to be the deciding factor on how noisy the exhaust is and the size of the actual Exhaust pipe. Some 3 chamber or 2 chamber Flowmasters would sound pretty good and I wouldnt take the exhaust pipe over 3" if back pressure will be an issue.

Buck

One of the things about the Corvette is that the pipes pass through "holes" in the frame/crossmember, so I would recommend some coated headers that are made for the Vette and a 2 1/4" system. The 2 1/4" pipes will fit better and not hurt performance to any noticible degree.
Corvette mufflers mount behind the rear end, so there are no tailpipes to dampen the raspy noise. For this reason, I would recommend something like a DynoMax Super Turbo or other fairly quiet muffler...A muffler like a FlowMaster will drive you crazy with the noise, plus the Flows for a Vette are really expensive. Heck, even stock vette mufflers sound pretty decent !!
A note of caution, stock manifolds will not fit on Performer RPM heads because of a ridge of aluminum on the casting...It hits the manifolds before you can snug them down, so have the headers ready when you swap the heads.