Nice piece. You should restrict it to non +P ammunition. Several ammo companies make loads specific to short barrel guns and should work well. A Tyler T-Grip would be nice as well.
A Cobra of that vintage has the long frame and Pachmayr Compacs won't work. It was the mid-'60s when Colt standardized all D-frames on the short grip frame. The Pachmayr Presentation grips will work as they're molded for both short and long frame Colt D-frames but that's getting away from being concealable. That's why I suggested a Tyler T-grip to fill the space between the frame and trigger guard.