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72-73 wiring and dash swap
Hello, I'm new to the site but I've been a long time browser. 

  I have 72 mustang coupe 302 c4 trans that I built over the years until a kid wrecked into the side of it. 
I caught a guy at a gas station with a 73 fastback 3 speed inline 6 on his way to the scrap yard. The car was in really good shape besides the interior was gutted and the wiring. I bought the car for 250 and I'm wanting to swap over all my wiring and new dash, new leather seats, and basically everything  from the wrecked 72 coupe including the v8, into the 73. But with the 72 being an automatic trans, and the 73 being a manual.. what wiring problems will I run into during this swap? Or any other problems I might run into? 

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Welcome from iowa. I did an auto to 5 speed swap on my 73. only wiring change was the reverse lights and bypass the NSS.

73 Grandé H Code. Headman long tube headers, T-5 Transmission, 3.70 Traclok, Lowered 1" all around, Aussie 2v heads w/ 2.19 intake, 1.71 exhaust, screw in studs, full roller cam 608/612 lift 280/281 duration LSA 112, Quick Fuel 750 CFM double pumper, AirGap intake.

- Jason

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The only difference is the harness for the Neutral Safety Switch vs the reverse light switch. Autos have the NSS harness, the manuals have a similar harness that has a loop for the starter circuit, and a connector at the shifter for the reverse lights. The harness plugs that connect to the main engine bay harness are identical, so you can switch them around as needed. The reverse light harness on the 73 will plug into the 72 engine bay harness and vice versa.

FWIW, you'll also need the engine frame stands from the '72, as the 250-6 parts are different. Trans crossmember interchanges though.

I think you have to put a jumper wire in one of the plugs at the back of the engine where they feed the harness to the transmission. I have faint memory of that. Midlife probably can say better than me.
Also the turn signal wiring on a 73 is different than a 72. The plugs do come off the end of the turn signal by pulling the red part out of the center. Allows the pin connectors to be removed to install a new turn signal switch.
Every car has sort a unique harness depending on what options are in the car. There is not a standard wire harness with multiple connections for under dash.
You should be able to unbolt the entire dash assembly and move over.
The 73 upper dash panel with the VIN# and pad has two additional screws not in the 71 72. They are just in front of the front edge of the dash pad. Phillips heads. The 72 main dash will not have a place for those screws.
So you will know every part of the car when you finish, lol. Lots to move but if you do the dash as an assembly it is much easier.
I would put new heater core in while everything is out of the way.
Not sure if coupe and fastback have same seat track or not. I know the vert is different.
Rear seat will be way different between coupe and fastback.
Not sure how you are going to handle the title if you swap bodies. The VIN# is stamped in both shock towers and of course on the Buck tag on the radiator support and then VIN tag on the dash. The engine is also stamped and the transmission but not the rear. I would ask your DOT about that one. You will have a fastback body but title will be coupe might be an issue. Better to check first than to do lots of work and cannot get title or tag.
BTW welcome to the forum from N.C..
Couple pictures of a Buck tag and also the partial VIN on the inner fenders.
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When a man is in the woods and talks and no women are there is he still wrong??
If it were me, I would just get a complete new modern wiring harness and start from there.

"I drank what?" - Socrates
I would get Midlife to refurbish and make any necessary revisions to the dash wiring harness. That way it will be a complete plug and play.

“If you can't explain it simply, you don't understand it well enough.”
--Albert Einstein
Can't swap 72 and 73 harnesses: ignition and turn signal switch connectors are completely different and use different style pins. Headlight harnesses must stay with the 72 or 73 grill system as parking lamp systems differ. Tail-light harness plugs are also different.

You got a nice parts car there...

Let me check your shorts!

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