Hey coilover...... read down to post #6 here. This is your complete pinout for the atlas. Looks a lot like a factory LS harness to me. All the same GM stuff. Orange wires are constant, pinks are all key on 12v+ and the injector stuff and O2 stuff all looks familiar to the harness that im used to building. You should be able to build a small fusebox with like 3 relays (main, fuel pump, fan) and a few fuses for the ECU, MAF/HO2’s, coils, injectors and you should be up and running. Will probably need someone with HPtuners to flash the ecu and turn off the factory VATS so it will start. Should be pretty straightforward.
Atlas Pinout
