Re: resoldering old double barrels
The problem is in the word "align". It sounds simple to just get both barrels sort of pointing in the right direction and that is OK for a gun that will be a wall hanger. But if the shotgun is to be used, then you either do a "good enough" job (like most U.S. factories did) or you go the whole way and do the job right. That involves soldering at the breech, then using wedges to align the barrels, shooting, adjusting the wedges, shooting again, and so on until both barrels "look to" the same point. It is that tedious and time consuming work that accounts for a lot of the high price charged for the best doubles. Colimators work, but the experts say there is no better way to be sure how a barrel will shoot than to shoot it.
If I wanted to just keep those barrels together for a wall hanger, I would remove the ribs, clamp the barrels with a steel spacer to keep the original spacing, tack weld the spacer and the barrels together, then solder or glue the ribs back on.