The BC WGRS will fit fine, it uses the 2 rear base mount holes. Be sure to clean the factory thread locker out of the mount holes, or the WGRS screws won't likely tighten up, they'll bottom out against the thread locker. The bottom of the mount holes should appear bright and shiny. I use a micro torch to heat the thread locker, then it's easy to dig out with a sewing awl or pointy tool. Dunno about the height of the factory sight, might take replacing to get it to work together, which if it's plastic, you'll probably wanta do anyway. :wink:
That Ultra stock will take some of the recoil out, add a small grind-to-fit Limbsaver, and you'll be all set!!! Well....maybe some weight in the stock bolt hole, too..... :oops:
Tim