Gen 4 ignition wiring questions

[DM72C20]

Getting close to finishing up the wiring on my swap. It’s a 09’ 4.8 from a Silverado going into my 72’ C20. I’ve reworked the original harness, retained most of the 09’ fuses, am using the 09’ alternator, modified the tank for the 09’ fuel pump module and am basically after a reliable daily driver.

What I am completely lost on is how to get the ignition switch inside the cab to communicate with the ECM to start the engine. It would be running through one of the 09’ relays - I tried a pink wire from the ignition switch to pin 30 of the run/crank relay. It clicks and the MAF clicks as well when key ON, but no crank. Coils have power and the fuel pump primes. I thought the run/crank relay would be the one to get the rest of the relays going in order to fire. But maybe it should be wired to the starter relay? Maybe I need the purple solenoid wire instead? I thought I read that the ECM needs constant power which is why I started with the pink one/key hot.

Going to get into HP tuners tomorrow to get rid of Vats in case that is interfering. I thought it would still crank with it enabled. Any suggestions would be great!! So excited to be at the stage of even trying to start this thing. I know lots of these swaps have been done, but my goodness what an effort!