Why not switch over to a Picatinny set-up?
With the "Tactical" rage these days, there are at least ten companies making rails and rings- best of all: they all interchange with each other, so you are not stuck buying so-and-so's rings because you have their base.
I am working on a Remington 700 P (short action, .308) as a target rifle right now. I have a Badger Ordnance 20 minute rail on the way, and some VERY inexpensive Leapers rings on the way as well. These were so cheap, I had to buy two, assuming the price was for one ring! I have not received them yet, but I got the medium (which should work fine) and the high (just in case) because they were so damn cheap. Extruded aluminum, four clamp screws, 1/2 inch nut to attach them to the rail. They look the business; time will tell if they are. If not, I will replace them and be out $10.00 rather than $100.00... I will not be dropping this rifle out of a helicopter at 100 MPH, so I do not need rings that can support a mid-size pick-up truck (neither does any other non-professional, but don't get me started).
Extended rails are available too- the worst case I could see is that you may have to get a 6" blank rail and have a gun smith fit it for you. Once the rail is in place, the world of optics are your oyster...
Since you likely will not be working out past 500 yards, and (I asume) you will have a 30mm tube on the optic, you can use a flat base (0 MOA) with no problems. On that magnum cartridge, I would expect it to reach 700 yards or more easily without running out of elevation. (the 30mm Leupolds have 90 minutes total typically)
My slightly more than two cents...