To follow up on several recent requests for info, and correlate info already on the board in slightly different form, here's the info on pin-outs for both radios and amps typical of the 1989-1992 model years. The connectors are the single, large (compared to the '99-up connectors) 14-pin offset rectangular connectors. The same connector is used at both the head unit and the amp, although with different wiring. The pin numbers are marked on the outside of the connector, with odd numbers on one side and even numbers on the other.
Basic info is from the "Green book" for the '92 960, which has been corroborated by experimentation with radios and amps from other period vehicles. Some wiring color may change from year to year, but the pin-outs have been consistent so far.
RADIO / head unit
Pin Function '92 wire color
1 +Dash L R-W
2 +Dash R GR-R
3 -Dash L W
4 -Dash R GR
5 speedo not noted
6 Dimmer Y-W
7 + Rheostat Y-W (connected with #6)
8 - Rheostat BN-SB
9 + Battery GN-BN (via 10-amp fuse)
10 GROUND SB
11 + ACCESSORY Y-SB (switched power)
12 + Antenna R
13 NC
14 NC

AMPLIFIER ( includes 4 x 20, PN 3533004, and 4 x 40, PN 1373082, possibly others)

Pin Function '92 colors
1 Ground SB
2 + L front Y-W
3 + R front Y-GR
4 + Battery P-SB
5 NC
6 - L front W
7 - R front GR
8 + L rear Y-BN
9 + R rear Y-SB
10 NC
11 + Battery P-SB (connected with # 4 via 15-amp fuse)
12 -L rear GN-BN
13 - R rear GN-SB
14 Ground SB
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We have met the enemy and they is us. [Pogo] S70 T5 cop car : Rough Rider suspension, Walmart fog lights, eBay speakers, ambiance by Pall Mall, trim by Le Duc d'Tape, 8-channel THD by OEM amps