Hardly any years have the same mapping. 87-88 are the only two I know that are close. :)

I have the 79 map. There are differences from '80 in the radio detail, but only insofar as the electric antenna is concerned. The '79 antenna was manually operated with an up/down switch, if you even had one, where the '80 got the relay operated antenna motor switched by the radio. There is no connector detail in the manuals, probably because it was too simple. Only switched hot from fuse #1 needed to operate radios from the '70's. Station memory was entirely mechanical. Speakers were front only. Anything fancier was dealer option or aftermarket add-on and not documented in Volvo's service lit.
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Art Benstein near Baltimore

Real Engineers consider themselves well dressed if their socks match.
Real Engineers buy their spouses a set of matched screwdrivers for their birthday.
Real engineers have a non-technical vocabulary of 800 words.
Real Engineers repair their own cameras, telephones, televisions, watches, and automatic transmissions.
Real Engineers say "It's 70 degrees Fahrenheit, 25 degrees Celsius, and 298 Kelvin" and all you say is "Isn't it a nice day?"
Real Engineers wear badges so they don't forget who they are. Sometimes a note is attached saying "Don't offer me a ride today. I drove my own car".
Real Engineers' politics run towards acquiring a parking space with their name on it and an office with a window.
Real Engineers know the "ABC's of Infrared" from A to B.
Real Engineers know how to take the cover off of their computer, and are not afraid to do it.
Real Engineers' briefcases contain a Phillips screwdriver, a copy of "Quantum Physics", and a half of a peanut butter sandwich.
Real Engineers don't find the above at all funny.