Keep the factory intake, I got an Edelbrock performer last year brand new and I am now trying to get my original manifold restored because the performer runners don't line up very well and are smaller than the factory egr manifold. Pontiac made them right the first time and is why there is not much to pick from for aftermarket stock style manifolds. Bigger manifolds will create clearance problems with the shaker hood.
The previous "how to build max performance Pontiac motor" book by Jim Hand explains cams pretty well. If you can get a copy of that out of print book it will help you wonders.
Use Google to search this forum, the Pontiac street performance forum and trans am country forum to get some hints on cams. Its asked almost monthly, commonly with 6x-8 heads.
I have no opinion yet on the can I picked ( I haven't finished building the motor). Here's a list of cams off top of my head that are popular... Xe262 (modern grind for low compression), summit middle cam, Crower 60918, or even the stock 068 HO cam.