The opening is different. It could be done but you would need to remove everything from the dash to do it, and at that point you might as well pull the whole dash.
I think the 69's have the key in the dash so I don't know about that. And I think you may need to do some cutting on the frame to make the rally dash fit but it should be able to be done with a little fab work.
I think it would be easier to swap in a 67-69 Barracuda dash frame. That way you can have the rallye dash and still retain your ignition switch in the dash.