I removed the swivels from a 1920's British boxlock that was in wonderful condition. I used wood from under the buttplate to fill the stock hole, matching the flow of the grain. I filled the rib holes with filler screws. I'm not crazy about the screws but tig welding the holes in the rib like my 'smith suggested seems like a lot of trouble and expense. I have swivels on a Husqvarna gun that I have left in place as they are appropriate for a European gun.