The correct model is 1883; and welcome to the forum, but I'm curious. If you have the skill and equipment to sleeve barrels; then why didn't you use the original mono-block and sleeve a new set of steel tubes into same? Using that method you could have kept the original 10-bore configuration, which I suspect were 30" tubes; or reduced to a 12 bore as it appears the original ribs were fine. That might not be an option now, as I assume you've chopped the top rib.