Dave, Easy fix. Weaver makes gunsmith bases that can be fashioned to fit about anything. Find a smith/machinist, have them mill the bottom of the base flat if it already isn't. Then have them mill a recess into the flat that is the same width as the rib on your barrel, about .050" deep. Now the weaver base will set nicely on the rib. The only thing left is to drill and tap 4 screw holes into the rib to hold it tight. In my shop it would take less than 1 hour, done.