i am also trying to get all the bugs worked out, from what i learned from John at spear tech the harness is truly plug and play. here is a link from what he sent me https://ls1tech.com/forums/conversions-swaps/583994-ls1-wiring-speartech.html
it seems pretty easy, as previously stated the ls1 will run on a garage floor.

 

You only need to connect the wiring for the motor. You leave the wiring for the rest of the car intact. You should not have to change any of the radio, lights or window wiring. You use the factory mustang wiring for all that. You just need to give the LS1 battery constant power, IGN + power, and a start signal. It will run if you take all the orange wires and hook them to battery power, all the pinks and hook them to IGN +, hook the large purple to the starter and a few grounds. That is a oversimplified explanation but it would run, the rest of the wires are for gauges, and other things that are not absolutely needed to make it run.

 

And I can scrap my mustang PCM? Or need to keep it as well for all that stuff to work... Sorry for sounding like an idiot but I don't want to kick my own *** when I sell something and then need it back lol

 

I am not 100% sure if you can scrap the mustang ECM, some of the newer cars use it to control some of the body functions (gauges, radio, etc). I have never looked into mustangs so I can`t be of much help there, unless you have wiring diagrams for the car. If you have wiring diagrams for it I could tell.

 

Maybe I will give speartech a call sometime soon. They seem to know what they are doing.

 

#1 retrofit swap rule: NEVER sell anything from either your swap car or your donor vehicle until your project is COMPLETE!

 

If we do your harness it will come back ready for action!

It will be complete with fuse block, fuel pump relay, check engine light, diagnostic port, etc. Hook up 3 wires and you're running! No running around the junkyard looking for a diagnostic port to try and splice in and wondering if you have the right wires. We take care of all of that so you get to enjoy your project much quicker.

 

Would u need both harnesses or just the my LS1 harness?

 

Just the LS1 harness. When you get it back you would need to find a battery source on your car, an ignition switch source on your car, and either run our wire back to your fuel pump or find the wire that presently goes to your fuel pump and splice into it.

 

And after that then we can rip out what I don't need from my mustang harness I guess? I just don't want all the extra weight of having 2 harnesses. And did u know if I needed to keep the mustang pcm in the car to make anything work?

 

I don't think the Mustang PCM is needed at all after the swap, but I'm sure Brains or some of the other Mustang swappers can tell you for sure.

 

omg definitely go efi. i can't believe how many people are going carb. i mean come one, we didnt invest all the time, money, and engineering to develop a technology that gives better fuel economy, better reliability, and a FLATTER power curve just to do something that's "easier" (which isnt even really true, efi tuning is just different, not harder). Please learn the wiring, else, find some one who does. It is definitely worth it!

 

im gonna run a carb on the LS2 in my mustang. but I am starting from SCRATCH. I don't have any EFI components except fuel injectors.

my car will be a stripped race car thats tagged and insured so driveability doesn't mean a ton to me. only things I want are an overdrive and lockup converter.

 

what G body said

you just run the existing mustang wire to the LSx starter and thats pretty much it.