Joey . . . an observation, correct me if I'm wrong.
You have a cylinder frame marked RUGER .357 CAL. BLACKHAWK and bearing what we assume is the original serial number. If you were to request a "letter" from Ruger on that serial number (a good idea) they would almost certainly advise you of when the gun was shipped and its original configuration. As far as Ruger is concerned it's still that gun. If you restore it to its original configuration matching the "letter" you essentially have that gun, with a few parts replacements. If you use a barrel length matching the original description, all is good, and there'd be no possible hassles from the BATFEIEIO upon a further transfer via an FFL holder. I assume that's how you purchased the frame. Looks to me like a perfect "restoration" of a neat old gun. All JMHO, of course.
Wonderful project. Yes, please keep us advised on your progress.

