Skip the ACOG, look at the RMR sight

The Docter brand seems to be more popular worldwide but the Trijicon is better known in the US. I have used both with no issues. You can get a better selection of hunting style mounts for the Docter while many of the mounts available for the Trijicon look very tactical/military. These sights have different footprints so they are not interchangeable between brands. Trijicon does make a adapter plate so Docter mounts can be used.

Verney-Carron uses a short piece of steel with a weaver type crossbolt slot, inletted in the rib. The head of the V-C shop feels that this is a more secure method for attaching the sight than milling the side of the ribs. I have spoken to a well respected double gun gunsmith in the US who while he acknowledges it is more secure feels the V-C system is overkill.
I personally like the weaver type base because if down the road you want a different sight you can more than likely find a mount for a weaver style base but may not be so lucky with the milled rib.

If you already have German pivot bases (ERA/EAW type) in your rib, several people make a mount that adapts them to using the Docter reflex sight. Using the Trijicon adapter plate (part # RM37) the Trijicon scope could also be used.