A 1960 would have had a plastic butt plate but it would have been curved. If it has a pad I would bet it has been cut because at the very least they would have taken the curve out. I had a 270 where they just took the curve out and put the pad on. I would guess the plastic butt plate would be about 3/8 so if they just took the curve out the stock would be about 13 1/4 to 13 3/8. If they cut it all the way down for pad it would be closer to 12 1/2 or 12 5/8 for a 1” pad. I assume you are talking about a standard 1” pad??