You may have to remove the front D-ring swivel (easy to do just drill out rivets) I don't know for sure. I recently got a Scout that came in a Urban Camo stock that was originally on a Socom II and the stock had no front swivel. I'm making the assumption that the bottom half of the cheese grater (my pet name for the Socom II rail) secures through those holes. Or at the very least interferes with the lower half of the cheese grater fitting around a standard FG stock. The "drilled and tapped" hole on the side of the receiver is the standard scope mounting hole that is on all M1A/M14 receivers.
Mind you this is only an assumption and you know what happens when you assume.... ass-u-meGI6 I've been curious myself on how they mount that thing.
The Vltor has two holes on the section of the cluster that attaches to the receiver but only uses one. It will probably line up and shouldn't be a problem. If you already have the cluster rail, see if it lines up with the receiver hole. The cluster rail uses a bracket attached to the barrel in addition to a pinch clamp near the receiver. As geeck mentioned, you may have to remove the forward swivel to fit the bottom cluster correctly. The only drawback to this would be the cluster rail utilizes the same hole needed to secure optic mounts on the receiver, so therefore you can't have both. Here is an earlier post that depicts the removal of the cluster system.
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