Evolution Gun Works Remington 660/600 Mohawk Picatinny Rail Scope Mount 40500, 40502. Evolution Gun Works Tactical Rails.
You can also use the Leupold STD mount with the Dovetail type rings. I'll say right up front I'm no fan of this style due to the monkeying around with aligning them. This setup almost always requires lapping of the rings as well. Good Picatinney rings that are machined as a pair are a lot less hassle. You can bet by with less expensive, non matched rings and still get away from the hassle of twisting the rings for perfect alignment. The straight rail takes care of that issue.
EGW rails are among the best.