vcav, I'm guessing of course, but I'd say that with the 422 stroker, vararam, Fast intake and Kook's headers you will probably be in the 500 to 550rwhp range.
As for the cam, I think you will need to decide first whether you're gonna run N/A or if you will be adding a blower or spray. If you decide to go with either of these power adders, your choice of cam will be different than with N/A. Also, if you decide to go blower, the heads should get some work to lower CR. That will determine the level of boost you can run. Remilling the combustion chambers at the same time as you get the motor built can save you considerable bucks if a blower is in your future.
I would also be hesitant to spray over a 200 shot on a stroker engine....but that's just me.
As for your 1 7/8" headers, I don't think you will get the maximum potential out of that mod unless you run 3" midpipe and exhaust all the way through. In my opinion, it doesn't do a lot of good to open up the exhaust with the headers only to place a restriction in the path with a 2 3/4" exhaust. Believe me, I hated giving up my Borlas but one mod ties into the next, if you know what I mean.
Best of luck on your project! Sounds like you are gonna build a true monster Z
Mike