Fairmont Squire System

Hi folks, I'm a newbie here, but not to DC auto electrics (was an Army Elect Tech, and am a serious car-buff) and just want to get my system right.

Here's what I've got (and don't):

A 40 watts/channel MEI amp (No diagrams - and none on the WWW)

A Toshiba cassette deck with 25 watts/channel (no user manual)

A Sanyo cassette deck (standard factory output) with shaft controls and old-style pushbutton controls.

A pair of 40 watt 3" in dash speakers

A pair of JVC 6" X 9" 100 watt 2-way mounted (I modified the side panels to upgrade from the smaller stock 6" X 8") and made mounts on the car's rear quarter sheetmetal to mount them.)

A pair of JVC 150 watt 3-way speakers - recently given to me in new condition.

I prefer the Sanyo unit because I don't have to take my eyes off the road to find a station or adjust anything. The Toshiba came in a 1978 donor car that I used to do a frame-up resto of my wagon, no manuals. The cassette deck works fine, but the tuner remains in Scan Mode, and I there's nothing even close to tell me how to use it. The Sanyo is a no-brainer.

I'll use the tips on figuring out the wiring scheme from this fine sticky:

https://www.the12volt.com/installbay/forum_posts.asp~TID~74637~PN~1

but the MEI amp wiring is a stumbling block. It's a PA705H with the wires all properly coded (EIA coding). The Sanyo is Model number FT 417 with the following wires (wierd connectiion block):

Near the antenna cable: Medium green - no idea for what?

Connection block is a round Bakelite type with 4 wires going in:

Black

Yellow

Green

Red

and one Red wire/ with white stripe looped back into the back of the HU.

The wires coming out of the round connector are:

Green

Gray

Yellow

White

Red

Black (taped over)

Blue

My last alternative is to re-open the Sanyo HU and trace the wires to the circuitry and match them up with Power, Ground, LH/RH, Instrument light circuits, but if anyone knows about these old ghosts, it would be appreciated.