AZ - I'd suggest using the Leupold Mount Selector found at the link below.

http://www.leupold.com/resources/Mou...rt/default.asp

Since this is a Leupold site, it will only allow you to select a Leupold scope. However, just select a Leupold scope that's similar to the Nikon Omega....like the VarX-III 3-9X40mm. The important thing is to select the Leupold scope on this site that has a scope bell similar to the Nikon Omega...I think that scope has a 40mm bell. Right?

A buddy of mine has an Encore set up with the Leupold QD bases and rings. I could ask him, but I'm almost certain he just went with what the Leupold Mount Selector suggested.

That's a heck of a rig ya got there

Hope this helps...