If they are indeed for the OMT you have, then they should fit ANY Colt E or I frame revolver.
Just be aware that after the mid '50s or so, Colt started allowing their rebound pin to protrude from the grip frame surface. Therefore, any grips on those guns need to have a "relief" cut for the rebound pin to fit properly. Much like the "relief" cut you see on the left panel for the rear sideplate screw, and actually you can see a slight depression in the same panel where the rebound pin is.
Those grips could be for a New Service if they are absolutely too big for the E/I frames, but I think what you are experiencing with the "over hang" is just the variances between frames. Most likely those grips were made and fitted to a different gun, then ended up on this gun. So the backstrap fit isn't perfect.