I was you would take old parts like this

http://egun.de/market/item.php?id=5302869
http://egun.de/market/item.php?id=5320390
or this
http://egun.de/market/item.php?id=5321875

and do what gunmaker here doing: material when needed is apply be welding and then its fit into the existing bases. they dont care for an allready fit feet because it never happen and change what they need by welding and file.