Hey Fern,
The bottoms are slightly different, but it is a conversion that really is not hard to do, and if done correctly, you will give the illusion of it looking totally correct for 1970. If someone who knew what they were looking at looked in your console at the ribs, that is the only way to see the difference, i think the screw tabs are in a different location and hieght, and i think their is an extra rib. You would still be able to use the hole as what a standard 1970 console hole was used for, like soundcontrol said, it is only to hold your seatbelts while not using your shoulder belts when driving.