Do you want to do this as a temp/test approach?
My suggestion to you on that would be to search for the S110/S111 splice point, if you see the blu/y conductor there as well instead of the gry/blk keep following that conductor to see where it (if it does at all) returns to gry/blk. The schematics we sent to you, mine IS the Ford schematic, what Ron sent to you is the same but the Ford schematic states the splice points, (perhaps Ron does have the actual ford manual which states where the splice points are, I've not got that for pre 98), go straight to the PCM as the schematic details to go to pin # 58. I take it that at the GEM pin #9 is the proper pin that the gry/bk connects to? The GEM is under the instrument panel behind the radio.
This will take some time, be patient....