Not trying to sell you on it, but with your cam change and head work it does seem that you are at least a little performance oriented. In which case I'd be looking at the 2 1/2" mandrel kits. But I'm one that likes to make them run as well as they look without sacrificing the stock appearances, so I'm a little bias.
My tests have all been done through the stock manifolds as well. There is a lot to be found with just the exhaust pipe upgrades with these cars. I talk to a lot of the PS guys, which is what my Formula as well as my Z was built to conform with. Rules allow a maximum of a 2 1/2" system as one of the few areas an upgrade is allowed, but they all run stock exhaust manifolds per rules. Most will tell you, no matter what the car or engine, that the exhaust pipes are one of the single most improvements made on their cars, and my testing has shown that as well. Matter of fact, a lot of engine dyno testing has shown that the biggest improvement in the systems are the down pipes right off the manifolds. That first bend off the manifolds is the most critical. Going from a crush bend down pipe to a mandrel bend down pipe, and no exhaust system afterwards on an engine dyno, has shown as much as a 12hp difference alone on some engines.
Crazy to think about, but thought I'd share.
I went with the stock tail pipes on my Z because I do want to have a stock outward appearance, as that's really all you see, the rest of the system can't even be seen unless you're crawling on the ground. But by all means, go with a reproduction system if you're looking for concours appearances and not that worried about performance. It would certainly be an easier system to bolt on and function perfectly fine.
