Bogen 3221 Tripod Removal

I have an old Bogen 3221 w/3047 head. I want to remove this head and replace it with an Acratech. Does anyone have experience with removing these? I discovered that the tube of the center column is press fitted to the base. There are 2 base plates- the one press fitted to the tube is aluminum looking and the one above that is painted gray. It look like the 2 plates are held together by 3 screws on the bottom of the aluminum plate. Do I just use something (?) to hold the 2 plate assembly and unscrew the head?

John