FWIW, I've done a little porting on the Colorado manifold as well and there's a lip on the roof after the entrance that responds well to the very minimal effort it takes to port it out. The inlet is also 79.5mm already.
Whether it'll fit on a Camaro, I have no idea. The 80mm throttle body will work well if you flip it upside down, connector should reach. This manifold also comes on 12-16 Acadia (but with a different lower aluminum section), 14+ Impala and 13+ Equinox/Terrain.