I don't think Ruger ever cataloged a 45/45acp Vaquero, least that is what they told me when I asked them if the could fit an acp cylinder to my Vaquero. Sounds like some one added an acp cylinder to your Vaquero. It is a sweet setup.
Ruger did not catalog a convertible Vaquero but they did offer in .45 Colt/ACP. I had one and just saw a very nice one for sale at a local gun show. They were limited distributor special runs for maybe Lipsey's? They might have been offered through more than one distributor. I think there were some offered in both blue and stainless, if memory serves, and in 4 5/8 and 5 1/2 inch lengths.