Since you're just wondering about it, it's an interesting question even since you don't plan to do it.
1. The free bore in the chamber is not an issue. Thousands of rounds of the short .45 Cowboy and also .45 Schofield (also shorter than 45 Colt have been fired from 45 Colt cylinders with no bullet shaving or any real accuracy issues. After all we're not talking about a target pistol here.
2. Recessing the chamber mouth .034" for the thicker AR rim, (.092" for AR vs. .058" for 45 Colt) could cause excess headspace for the 45 Colt. Since the rim diameters are nominally the same, the 45 Colt rim could go partially (.034") into the recess causing the case mouth to headspace on the shoulder in the chambers. Depending on the exact depth of the shoulder in the chamber and the amount of crimp on the case mouth, the 45 Colt case rim may be too far away from the firing pin (excess headspace) for reliable ignition or may not. A strong hammer spring and enough firing pin travel may be enough inertia to fire the 45 Colt in spite of the excess headspace.
But we don't know until we try an experiment in your particular gun. I just turned the rim down .034" of a 45 Colt case from the front side, to the case wall diameter and installed a primer. I crimped the case mouth in the bullet seating die but w/o a bullet installed. The case then went into the chamber far enough to simulate a chamber mouth recessed .034" for the AR rim. Fired it in my New Vaquero 45 Colt gun to see if the primer ignited. It did. But it was a very minimal primer indentation. So it's not likely to be reliable for all primer brands or in every Ruger.
Here's a thought: modify the AR cases. if you have a lathe or know someone that does, turn down the rim thickness as I described above on your 200 cases. You not only can shoot them in your 45 Colt, you can reload them and keep shooting them in any 45 Colt revolver.