Neal Rice made some adapter mounts, that would take a Redfield style ( Highpower style) sight and mount to a Unertl type base. The base was mounted on the barrel, and the adapter extended back over the action. I use one on a highwall. The question is, would  the adapter extend far enough to provide proper eye relief and clearance on a lever gun. 
To get sufficient elevation the front sight must be mounted as low as possible.