Jim, What you need are Lyman "O" and Lyman "E" blocks, or equivalent blocks made by Unertl and others. I think there are some new production blocks available. A search for scope blocks on the internet would probably find the source. The blocks you need will have a small half moon shaped cutout on the edge. Original O and E blocks have become expensive, $100 or so a set, due to people buying them to use in making fake 1903 NRA Sniper rifles.