Oz,
P.S.- Another good gun in an over and under to convert would be the Ithacas in a 500 or model 600. They have the kurstin locking system on them that is a double crossbolt. As shotguns they run a little heavy, but converted into a 45-70, or something like that, I think they would be just right. Don't forget the 20 gauge bore rifle either. They do great things when loaded with Lyman hourglass slugs and pushed to 1400 FPS or better! 12 gauges are a natural to convert to 20 gauge rifles because you have more room to get things done correctly, and most of the extra weight is between the hands. Bob H.