My 1990 744 has an afermarket stereo installed. I need to remove it, and replace it with another.

From what I understand, the Volvo used a custom stereo, with a separate amplifier. I've got one speaker channel not working, which could be the stereo that's in there, but maybe not, so I need to find out.

First question: where, on a us (Left hand drive) 740 would the amplifier have been located? I want to be sure to get as close to the original wiring as possible.

Second question: Is a 760 wiring diagram for up to 1989 adequate for wire colors & functions for my 740? That helps a lot, but if something was different, I'll have to find another book.

Thanks!