I cycled through so many high-mileage used Volvos that I no longer remember the details, so apologies in advance. These radios came out of two different 740s that I owned. These are obviously OEM so if you’re looking for this style radio, either of these should fit. Serial number info from photos should confirm if it will work for you.
Both radios have a female CD port in the back, so the 6 CD changer should work with either. I only used it with one, but I forget which one.
Both also have anti-theft codes, included!
Note that the cassette player does NOT work, but who knows, it may be fixable.
With the CD model, you have access to 7 different CDs, one in the HU plus 6 in the changer (sorry if that is obvious). The upside to this changer is that you don’t need space for it in the dash. It should fit under one of the front seats for easy access, but you're on your own for a cable. For some reason this changer was installed in the back of my 740 near the spare tire making it very inconvenient to change discs.
Make me an offer, pay for shipping, offer them a good home and all three of them are yours!