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Depends. If you have a trunk-mount radio and you are already remote head to begin with (implied by the A9 head), then you find an A7 head with the remote-mount body on it's backside and just plug it in, and bitbang the radio. If you are not running remote (i.e., you make the radio a Dash mount version where the head and the radio are one piece), then you need to replace the DB25 control-head face place with one that plugs between the head and the radio itself. See Mike B.'s website at onfreq.com.