Okay, it's a Bravada, close enough!
It cranks but won't start. None of the idiot lights come on, nor do instruments. Fuel pump doesn't prime, Turn signals don't work with ignition on either. I've pulled and inspected all fueses. I replaced the ignition switch, thinking that was the problem but no luck. When I removed the old ignition switch I only unplugged one clip on the column but noticed another clip about half way up the harness. Is this unnecessary? I can't find anything to connect it to and don't remember unplugging it.

I'm now thinking the ECM unless it's this 'spare' wire. Any help would be great!

Okay, it's a Bravada, close enough!
It cranks but won't start. None of the idiot lights come on, nor do instruments. Fuel pump doesn't prime, Turn signals don't work with ignition on either. I've pulled and inspected all fueses. I replaced the ignition switch, thinking that was the problem but no luck. When I removed the old ignition switch I only unplugged one clip on the column but noticed another clip about half way up the harness. Is this unnecessary? I can't find anything to connect it to and don't remember unplugging it.

I'm now thinking the ECM unless it's this 'spare' wire. Any help would be great!

If it's a two wire connector, I have the same thing in my Blazer unconnected. (I think it could be a remote starter link?)
I've also had my EEM take a crap with symptoms similar to a bad Ignition switch. I replaced the switch and had all the problems you describe.
Check the voltage at the top of fuse #24. If you have 12volts, it's most likely the EEM/ECM.