fwiw... when i purchased my '73 es in oregon in '03 it had a non-original cassette player radio installed(poorly). the p.o. had use a dremel tool to enlarge the dasboard holes. anyway i got a proper volvo radio (mono am/fm*)from e-bay and installed it but did not wire it... i found that the area foward of the stick will accomodate a new radio pretty well. it is secured with some bungees and a little velcro. then i just but a dark bit of cloth over the assembly and it isn't noticed at all. i prefer a cassette player to a cd player because i can check out cd's at the library put 5 of them in my 5 disc player at home and do a random play while recording onto my home cassette recorder. so i get more of a variety while playing the results in the car....
... the oem volvo radio can be wired at any time, maybe with switch to select either radio....works for me....
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*american music/foreign music