OK, I made the harness and got everything installed. It works and sounds great. The Axxess harness pinout matches my factory pinouts. I have the teal and tan connectors. I made a little document that details how I made the harness and routed it in the truck. Its a little chaotic, but I think you'll get the picture. Feel free to comment or let me know if I got something incorrect. I can edit and repost. Note: If I had it to do all over again, I would have cut the wires on the Axxess harness shorter and soldered everything . . .
I used all kicker that Crutchfield sent me including the CXA360.4 amp and the Kicker sub and amp made for GM. All in all it sounds so much better. I just need a little more control than the dinky head unit EQ gives me to tune everything. I would just add an LC7i, but the subwoofer uses speaker level inputs only as far as I can tell.
2021 Amp and Speaker Harness V1.pdf