That level of detail was available in the engineering diagrams from that time. Some years and model lines have been published as assembly manuals of late. Haven’t seen anything specifically for E-bodies for any years as yet, closest you will come to a ’73 E-body would be a diagram for a ’72...
Factory service manuals, have a collection of them from around that time. Fairly easy to get originals, reprints or digital versions from various sources including Ebay.
Mymopar.com has some free downloads, but they don't cover all brands/years.
First, I gave up on these cheap reproduction T/S switches years ago, mainly for durability issues at the switch head. They are junk, won’t have anything to do with them anymore. Yes, the dimensions of the connector are out of tolerance as compared to the originals. They can be forced together...
Originally the steering column wiring just connected to the dash harness just to the right of the column, never saw them wrapped up over the top of the column from the factory.
Some platforms/years used plastic slip isolators on the column support mountings, those had a ground wire from the column to the support to ensure horn switch circuit continuity to the body. Assume your ’73 E-body is the same as the ’70 I am currently working on, no plastic isolators, no ground...
Reinstalling the dash involves removing those two studs from steering column support, installing the two lower side captured washer 5/16” side bolts partially, leaving them stick out a bit. Place the dash frame’s open lower mounting flanges onto the bolts and rolling it up into place and secure...
Review post #6 of this thread, third picture. And post #15. The later metal valve you want is 3502723. The Bakelite valves proved to be very troublesome, the factory switched to the metal version around '73.
Door switch ground circuit, would connect to the optional ignition switch light delay relay and harness if equipped.
Dash light circuit
Radio power connector (accessory circuit) with dash light (orange)
Seat belt waring light
Goes to the blower resistor, non-A/C. Should be an additional...
You have the wrong version of that valve for an E&B body application. There are two versions that operate opposite of each other in function as related to cable movement direction. Note the slot orientation in the operating lever. You want the one on the right.
Now separate the fuse box from the bulkhead connector and remove the two Packard terminals on those two remaining A/C harness wires from the bulkhead connector.
Second pic is the rear body harness connector.