Not getting power to the ignition.

On an aftermarket harness, without seeing some of it, anybody's guess.

If you had the column loose to get the cluster out, or even if you didn't I'd check the neutral safety switch, it may be out of adjustment if you moved all that

Check that you didn't knock loose a harness connector. Did they eliminate the bulkhead connector? Check that.

Wander over to MyMopar and download the two sections for the free 73 factory service manual, which by the way got there because of guys on here. Also go to the wiring/ wiring diagrams section and download the 2 page aftermarket wiring diagram, which is not as detailed but might be somewhat easier to follow.

I say this because even though you have an aftermarket harness, the switch/ starter relay/ neutral safety should still be wired the same.

I'm assuming the key turns on "other stuff" like acessory? In other words exactly what does/ does not work?

The functional path for the starter is..........ignition switch.........twist to start.........power on the yellow "start" wire........out through the firewall.......to one flag terminal on the starter relay.......out the other flag terminal........down the firewall to the neutral safety switch center terminal.........grounds the relay in park or neutral