Bill,
I ordered the express sight from Ruger.
Go to the Ruger website, select customer service and parts ordering. You can get the parts ordering number for rifles there.
The Ruger express rear sight actually fits into the rear sight dovetail using only finger pressure. I will be using two different types of Locktite compounds, one for the threads on the rear sight locking screw and another to set the express sight in the dovetail.
I'll post all the sighting in info once I can get to the range. I will be doing all my shooting over Long Grass shooting sticks to mitigate some of the effects of recoil. I had shoulder surgery 18 months ago so I have to give it a fighting chance.
I am hoping I can regulate the elevation by ordering the required front sight blade from NECG.
Send me an email to the address in my profile and I'll send some pictures I just took of the express sight installed on the rifle.
Hope this helps
Tom M