I used these for reference:http://www.camaros.net/forums/showthread.php?t=121095&highlight=Intake+Manifold+Gasket+Alignment+Toolhttp://home.teleport.com/~cosa/vap/tech/inmanifold.htm
Best posts yet I've found on the subject. Following these provided a good installation with no oil leaks.
For machining the intake (which by the way after all this effort I'd true any original intake before I'd use it) I used the Supertuning Your Z28 Camaro book by John Olham.
Goes as follows; Table 5-2 Cylinder head .005", Side .006", Bottom .009". head .010", side .012", Bottom .017".
My machininst took about Side .012", Bottom .017" and that barely cleaned up the corrosion at the water crossovers, It left enough gap at the rails for a good seal.