Since the 721 has been out of production since 1962 I doubt many if any stock suppliers have that action to verify the inletting. From what I know the action screws are on the same centers but I don’t know about length. How the action screws line up with the bolt handle, safety and trigger I can’t say. I suspect that any stock would require some inletting work.
I would stay away from any aluminum bedding blocks. Wood could probably be made to work. As for the Archangel, I would be concerned about the magazine figment and just how much work might have to be done.
Whatever you decide, I would contact the fabricator first.