For any of you looking for a lower profile option than the factory picatinny rail to mount an optic utilizing a Trijicon RMR footprint, check out MachineCraft Replicas' R8R.
The fit and finish are perfect, and Dakota is a great guy to work with...
...especially if they are pinned and/or recessed. So far, the collection (ignoring "modern" variants and autos) includes: 60, 67-1, 66-1, 629, & 686-1. I'm looking forward to learning more about this era of revolver here.