Fantastic weekend at the ONSC Christmas party seeing my extended family. The Barn is a special place and I would drive double to just spend a few hours. It was awesome seeing everyone and Several asked how's it going on the 60 5.3 swap. Currently sorting through some issues since getting back from the exhaust shop and here it is laid out.
When I got home the next day, I pulled it off the trailer and had Jack idling in the driveway. Now that the O2 sensor is connected the ECM was able to go into "learn mode." I was working in the garage, frequently checking for leaks, temperatures, sounds, etc. The engine shut off between 30-45 min. After a failed re-crank, I went through checking fuses and traced it back to the fuel pump relay.
Referencing the Holley wiring diagram, Pin A2, in Plug P1A, sends 12v to the FP relay, opens the relay and then sends 12v to injectors, coils, and the fuel pump. The ECM is set to a 5 sec prime from pin A2, where 12v is sent to the FP relay to build fuel pressure. This all worked correctly. The problem I found is, after priming, the ECM is supposed to send 12v from pin A2 when it sees RPM from the crank. Cranking RPM is between 153 and 191. This should be plenty for the ECM to open the Circuit. Holley tech support agreed and said it had a "dead circuit" and had me ship it back.
Update. Spoke with Holley and they confirmed what I had found. New ECU was shipped out today.