$EE Impala SS PCM/Drivetrain in my 63 c10.

Scanner shows the o2 sensors stuck at 453mv. They never switch. Verified good AC Delco o2's by sticking them in my other LT1 car. Verified heater circuits by comparing sensor body temps between the 2 vehicles both well above 100* after a minute or 2 of key on / engine off. Verified continuity of PCM pins between o2 connectors and Clear Pins 7&8, 19&20 all measured 0.3>0.6 ohms. I've also tried my spare PCM. I'm using tuner pro to edit the files and eehack to flash and log.

I know its running pig rich, I can also command a really lean AFR and it seems to lean out and die based on smell (I don't have wide band.), with no change in the o2 numbers.

Short of replacing the entire wiring harness, I have run out of things to check and or try. Anybody here have any experience with this or thoughts?

Help me please.

-Brian