Wiring harness
 

Kind of a messy question so bear with me. I'm wondering what differences there are between wiring harness for a 67 six cylinder, manual, with no gauges, only lights compared to a 70 350, manual with full tach dash. Can I swap the 70 harness and dash into the 67? For example, is the 67 temp sending unit for dummy lights different than the 70 with gauges? I understand the 70 would have side marker fender lights and 67 would not. Ignition would have accessory on 70 vs 67 that does not. No AC in either truck. What else is different? Thanks for any help.

Re: Wiring harness
 

The wires to the sensors, coil, and starter likely will be a different length. The guages use different senders than the dummy light senders. (Dummy light senders are actually switches)

On 67's the front turn signal/parking lights use a 67 (Maybe earlier I don’t know for sure) connector that won't plug in to the 68 and up harnesses.

The wiper switch is on different sides of the dash bezel between 67 and 70.

Re: Wiring harness
 

Can't speak for sure about these trucks, but in most everything GM the plug for a dummy light dash and a gauge dash is the same but a lot of the pin locations are different. I would think if you swapped oil and temp sending units and used all the harness and the dash cluster together then you should be fine.

Re: Wiring harness
 

The fuse panel arrangement/mounting is totally different on 1967-68 versus 1969 and later.

1967-68:

https://67-72chevytrucks.com/vboard/...1&d=1735920032



1969-72:

https://67-72chevytrucks.com/vboard/...1&d=1378855171

Re: Wiring harness
 

The front turn signal light connectors will be different.

Re: Wiring harness
 

Idiot lights are controlled by switches -- ON when oil pressure is low and OFF when it's OK. Just the opposite for coolant temperature. So you will need oil pressure and temperature "senders" from a 70 truck to drive the analog gauges.

Also you will need to dig into how the ammeter (actually a +/- voltmeter) is connected to the wire running from the battery to the "splice" on the drivers side of the radiator. It's a bit complex to explain. Hopefully you can use the wiring from the 70 truck gauges as-is.

Re: Wiring harness
 

I put a 70 harness in my 67, as others have said there are some differences you’ll have to accommodate but it does work. The things that stand out are: pigtails to the turn signals, engine harness wire lengths, the wiper switch location in the dash, and the ignition switch itself needs to be swapped to the newer style.

EDIT: to answer a couple of your questions directly…

I think I just cut the pigtails for the fender markers off. I spliced in the odd 67 connector that runs through the core support to the running lights.

Sensors I just swapped out to the correct ones for a “gauges” truck.

I assume you’re using the 70 gauge cluster, it should plug right in. I didn’t, my 67 had factory gauges and I reused my cluster, it worked perfectly.

I swapped to HEI and internally regulated alternator at the same time so I modded the harness for those.

Something about the pinout on the ignition switch is different. The 67 unit will plug in but something didn’t work right (can’t remember what). Just use the newer style switch.

Early trucks the fuse box is horizontal, 69+ it’s vertical. It still bolts in just fine without modification, the lettering is upside down though.



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Re: Wiring harness
 

I put a 70 harness in my 67, as others have said there are some differences you’ll have to accommodate but it does work. The things that stand out are: pigtails to the turn signals, engine harness wire lengths, the wiper switch location in the dash, and the ignition switch itself needs to be swapped to the newer style.
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Re: Wiring harness
 

Also one of the biggest issues in using any other year harnessing is 67 is all the plugs. If you look at the males and females you'll notice that (the pigtail blades j mean)

Re: Wiring harness
 

You may not like my .02 but I would scrap the both of the old harnesses and buy a new aftermarket harness that matches your 67. Again just my .02.