1967 GMC - SWB, great patina

[WorldsCrappiestTruck]

Spaghetti for dinner.

Frankly for anyone doing a custom harness, I’d recommend to remove ALL wires from the PCM, cut ALL wires from the block that attaches to the underside of the fuse panel (mostly pink power wires) then sensor by sensor pull wiring apart until you get each sensors wire by itself. Black/white wires (GND) are jumpers together a few places but those can be lengthened again later.

Once each plug is free, plug in your connections, start routing wiring as you see fit - you’ll tidy it up at the PCM and fuse / relay block later.