If it has been hot blued I would assume that the ribs need to be removed, cleaned up and resoldered in place.
If the ribs have to be reset as AmarilloMike suggests, you might want to budget for rebluing them, too.
Still, that would wind up with you in it at less than a 0 frame 16 normally brings.
One more thing: I'd only buy "on approval" (i.e., you can have it checked out by a good smith on your dime) and that would include a good inspection for minimum wall thickness, chamber length and possibly over-reamed chambers (if they were lengthened).
