So last night it was cool enough in the Garage to finish this project. Spent four hours wiring up the power and mounting the PSU. I doubled and tripled checked everything and powered it up for the first time. The Pi4 didn’t post IE: nothing came up on the display.
As I was about to turn it off the magic smoke let loose from the Pi. I quickly pulled the power and even after a minute later I reached for the USB-C power connector from the Pi and the cable was very hot to the touch and felt like a freshly cooked spaghetti noodle.
So that means something shorted out and that Pi had a bunch of current passing into it.
Now I am out of a 8GB Pi 4. The only thing I can possibly think of what shorted out was the GPIO Breakout board. I didn’t use the supplied ribbon cable and used an old PC IDE ribbon cable. However I could of sworn I did a continuity test with it when I first hooked it up.
I’ll probably buy another Pi and try again.