Welcome to the Forum Chinook3!
You've gotten a jewel there. I'd take mix-ups like that any day!
You can get the parts to restore it to it's "as shipped" original condition. It may cost a bit,, but it's worth it. The differences in the original action and the transfer bar safety is significant to many of us. The original action has a sweet feeling distinct 4 click action. BUT,,,,,,,, to be safe,, you never carry it with 6 rounds in the cylinder. In the OM's like that,, the firing pin can be in direct contact with the primer of a live round. And if struck hard,, it could discharge.
To properly load an OM,, you open the loading gate,, cock the hammer to the half-cock position. Insert (1) round, skip the next chamber, then load (4) chambers. Then fully cock the hammer, and slowly & carefully lower the hammer on an empty chamber. NEVER LOWER THE HAMMER FROM THE 1/2 COCK POSITION! That will cause the dreaded "cylinder ring" mark.
A transfer bar action,, which was offered free to anybody with any OM Ruger SA,, allows the gun to be fully loaded with (6) rounds as the gun has to be fully cocked & hammer locked back for the transfer bar to rise up enough to allow the hammer to hit the firing pin when the trigger is pulled. If you look at all the New Models,, you will see a "stepped" hammer. The original hammers were totally flat on their face. The biggest drawback of the converted OM's is the "feel" of the action. Nowhere nearly as sweet & smooth as an OM.
And to clarify a comment made above; "Ruger started with serial number 1 on all of their old models." This is not quite true. The OM .45 Colt Blackhawks were not made until AFTER the 1968 GCA where they all had to have a specific serial number. Ruger added a "prefix" to their guns after that law was passed in 1968. The OM 45's were first made in 1971.