PCM wiring harness

[switchkid0]

I have a '97 F350 with 5 speed.
Died going down the road, and then no-start.
I checked the fuel bowl, fuse 22, and the HPOP reservoir.
I replaced the CPS, IDM, IPR, burnt valve cover plugs.

Still nothing, so I had it towed to a friendly Ford dealer.

They say they can't run a complete diagnostic, because there is a short in the PCM harness. I think they mentioned "block 40".
I can't possibly pay them $600+ for the harness, and $300+ for the labor to install it, which is what they quoted me.
Is there another source for this harness, or does anyone know what this "block 40" is or what it controls?

Thanks for any help you might be able to provide.

[ryandamo]

did you check the wiring harness under the valve covers?

[switchkid0]

Already replaced the valve cover gaskets, harnesses, and pigtails.