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Hello y'all, i am in need of a new wiring harness for my 67 Chevelle LS2/ T56 swap. The wiring harness im talking about goes on the firewall. I'm on a budget and wanted to ask a question to members that have replaced there wiring harness. What wiring harness did you use? Painless Wiring harness? How many circuits?
 

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I'm stuck here to . I went with Speartech and had my LS1 harness from a 2001 F body modified. WHERE EXACTLY is the proper place to route through the firewall on a 64-7 A Body? And using the stock harness WHERE to place the PCM? on the glovebox?
 

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on my 69, I used an LS conversion harness from PSI conversions that came with my engine and a generic 18 circuit painless harness for the rest of the car (lights, accessories, dash, etc). It took a little more thought to combine it all, but still a lot less than buying the painless harness for an LS. I mounted the PCM on top of the pass inner fender up under the outer fender so it is hidden. I closed off the original firewall fuse box feed thru and ran the harnesses out at the toe kick near the dimmer switch so they are almost hidden down low on the firewall when looking at outside.
 

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on my 69, I used an LS conversion harness from PSI conversions that came with my engine and a generic 18 circuit painless harness for the rest of the car (lights, accessories, dash, etc). It took a little more thought to combine it all, but still a lot less than buying the painless harness for an LS. I mounted the PCM on top of the pass inner fender up under the outer fender so it is hidden. I closed off the original firewall fuse box feed thru and ran the harnesses out at the toe kick near the dimmer switch so they are almost hidden down low on the firewall when looking at outside.
Joe you had to run a harness that was custom made (longer) for that huh?
 

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I have a Painless 20102 kit that I started to install on a friends project that he backed out of. Will let it go very cheap. Send me a message if interested and I'll fill you in with the details.
 

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I extended the wires from the computer to the dash and fusebox by about 6 ft. There were maybe 20 that I has to stretch. If I wasn't trying to hide the PCM and all the wiring, I would have probably mounted the PCM on the engine side of the firewall and it would have probably reached,
 

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I also went with PSI conversion. Those guys are great and any help I needed, they were there to walk me through it. It was a simple plug and play.
 

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Painless "NO". I bought an LS2 out of an 06 Vette. I got the computer but not the harness. I bought a Painless harness from Summit but, when I sent the ECM to Painless for the free "re-flash" to remove the un-needed features, I got into it with their obnoxious tech guy who told me that ECM wouldn't work with my engine (the ECM and engine came out of the same car). I sent the harness back to Summit.

I later bought a complete set-up from Speartech, which included Harness, ECM and pedal and, the speartech harness was in a loom. The Painless was not in a loom. That kit would be about another $150. I haven't installed the Speartech harness yet but, so far, I'm impressed with the quality and their customer service.

I also haven't decided on where the wires will go through the firewall yet. I'm thinking I'll put the ECM and TCM high on the firewall under the driver side fender. I've mocked it up and it seems to fit - pretty much out of sight when the fender is installed.



 
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My Speartech harness came with two 2" rubber gommets so, after a little more thought, I decided to run the wiring inside through here - into the cavity behind the drive side kick panel



and then in here, through the driver side kick pane- just above the vent opening.



I'm pleased with the way it came out. Looks like all the wires and plugs will reach where they need to go.
 

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I also have a speartech harness. The ECM is mounted on the passenger side of the firewall about where the feet would sit. I figure there will be a bulge there with the carpet, but it should be alright. Now I have to mount the fuse block from speartech and the check engine light.

I would rather not use self tapping screws to go through the firewall from the inside out. I don't want bolts showing through and looking bad. How do you guys mount these fuse boxes and make it look so clean? I have been searching the web but not coming up with anything. Thanks for the help.
 

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I welded some studs to inside of firewall before painting. if engine side is already painted, you might be able to use epoxy to attach studs to inside or make a bracket that attaches to structure inside (maybe kickpanel or the existing fusebox mounting points) to hold fusebox.
 
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