I have written Wiegand regarding a base for the new Flattops. We are in the middle of exchanging Emails. If I learn anything definitive, I'll post that information.
Thirty years ago, way before S&W started drilling and tapping their revolvers, I wanted a hunting scope on my Model 29 (8 3/8" barrel). I wanted to mount the scope in between the sights for a "barrel heavy" installation and to allow me to remove the scope and use the iron sights if necessary (busted scope or bad weather). I had seen a picture of one that Bill Wilson was offering his customers. I bought a 12" blank base from Kimber (later became Warne rings) and a set of rings. I had a local precision machine shop install the bases (after he milled them to my specs) with 8x40 screws. 8x40 screws have twice the shear strength of 6x48 screws. I have put over ten thousand rounds through that combination and have had absolutely NO problems.
Brownell's has blank Weaver style bases in both aluminum and steel (the steel will have to be blued). You could do the same thing with your Ruger, that I did with my S&W.
Another possibility is to contact SSK regarding a mount:
http://www.sskindustries.com/handgun.htmSSK has a dandy scope mount (Tough SOB) that I believe they can install for you.
If I were doing it today, I would opt for a good Red Dot sight. They are much lighter than a scope (lighter means less recoil problems) and work extremely well in both bright and dim light.
FWIW
Dale53