‘15 1500- No engine start

[PiggyNOX]

Hello , new to the group thanks so sorry if I’m posting to wrong group or if question has been asked before. My issue is that I bought a ‘15 1500 WT 5.3L that had around 350k with lazy #7 cylinder. So I bought used motor with around 100k from a ‘15 gmc 1500. Swapped motors out and when I went to start up I don’t get any crank, No gauges work, service error lights all come on. I’ve checked to make sure grounds are clean and tight, checked fuses inside cab and in engine bay, battery tests good, getting codes U0100 and U0102 and I’ve also installed new:
-Engine Harness (found some splits on harness that came with motor so bought new one)
-Computer (also have the original and one that came with the motor and I’ve tried swapping all 3 to see if that worked)
-Relay panel in engine compartment 
Just seeing if anyone has any fix’s or tricks. Thanks

Edited March 9, 2022 by PiggyNOX