73 Charger Engine harness help needed

[ODZKing]

I have asked a couple fellows with 73's about this as well but thought I'd post it here to see if someone knows right off the of their head.
I have a question about the engine harness and harness that plugs in below the wiper motor.  I'm told this is a 1 year ONLY on these cars. 73 only with 400 automatic and A/C.
I purchased a new engine harness and am having problems understanding what is happening here.
The PO dug into the old one and somehow tied together the main harness with the plug (I call it a half plug) which is below the wiper plug on the bulkhead connector. Someone installed a MSG ignition on it and what a mess it is.  I thought a new engine harness would solve my issues but it created more confusion on my part.
What I need to know is are they in fact tied together or are they separate.
Bill Evans at Evans Wire Harnesses says they are separate, one year only and that smaller bottom plug is part A/C and transmission.
Anyone know for sure?
I also have Randy73 taking a look at his for me.
Thanks

[randy73]

Expect a call this afternoon.

[Nacho-RT74]

mmm not sure what exactly are we talking about but I'll make a fast overview on engine and tranny harnesses useage on empty cavities

71s got one empty cavity on engine and 2 on tranny harness. These last were used for AC compressor ( blue ) AND blower ( green ), for a while engine cavity was left empty

from 72s up to 74s, the seatbelt system needed to send a ground gear signal to the cab, for seatbelt warning system. Then used one of the tranny harness cavities for this. On 72s and 73 then used the engine harness empty cavity for AC clutch blue wire, and the tranny empty cavity for blower, no matter if AC or just Heater. On AC cars then, got the AC harness splitt between both bulkhead plugs, needing to remove terminals from plugs if want to full remove any of the harnesses

on 74 however the interlock system required a dual start yellow wire setup on engine harness. This made to get the engine harness full used and just one cavity left on all bulkhead conector on tranny harness. Factory preffered then use a Grommet to feed all the AC system through firewall. I GUESS on heater, where just blower wire was required, the tranny harness cavity was still used for this