Magnum swap starts, does not run
It lives! Turned out to be crank sensor wiring. It's still not 100%, but it idled for 10 minutes and now I can check codes tomorrow.
When I swapped the connector for the crank sensor, I thought I had everything right, but obviously not. We just started swapping the wires around until it fired. I'll check my notes in the morning and post what wires go where on the sensor.
The previous wiring must have given the PCM just enough signal to fire, but not in the correct timing.