I remember those gooseneck radios well. They were considered state of the art at the time and rather expensive. Kind of the ultimate accessory for the ultimate driving machine (BMWs were all the rage at that time). I seem to recall someone on Xweb once posted pics with one in his X.If you don't want to cut the dash on 1300, you could get an 80's gooseneck Blaupunkt. Like the Dallas SQM88/Denver SQM108. Picture for reference. There are components to the system as well like a home stereo but you don't have to have them. CCP08 cassette shown but there is a DAT player and a CD player as well along with amps and equalizers.
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Your mention of "DAT" players also brings back memories.