You might want to think twice about this. The 'Unertl' target scope blocks were used with mounts that allowed the long-tubed scopes to slide forward under recoil, so there was very little stress on the blocks. Since the blocks were usually mounted on the barrel, the screws securing them were small and tapped into shallow holes. Barrel steel is commonly much softer than a hardened action.
Add these up, and putting a heavy mount with a modern scope onto these blocks with a rifle having appreciable recoil might result in the blocks getting loose over time. If you are planning to use the rifle for target shooting, you might want to stay with the original scope type. There are lots of Lyman targetspot, Lischert, and Unertl scopes with their origial mounts available used, though prices have gotten high. Leatherwood also has their 'Malcolm' scope new, which would be a direct fit on your blocks.
