I have a 66 Belvedere with the original wiring harness. I have had problems with the head lights, dome lights, tail lights, wipers, instrument panel. Just problem sometime shake a wire and fix it something more. Well my question is which is better year one original harness or painless performance harness.? The car is not original its a restomod I have a 6.1 hemi installed, 727 torqueflight trans, custom stereo system, 140 amp alternate. All help welcome.

YO is $$$ but will connect right up , Painless will be less painful to your wallet but require work to install , probably not a plug and play like the YO harness will be .

I've had nothing but problems with YO harnesses. They are cheaply made and the pins break easily. They also don't fit right in. The ones I worked with had plugs that fit way too tightly for the cheap pins to go in without breaking. They might be fine if you redo the whole car but if most of your harnesses are factory and you try to add the YO, in my experience, you'll regret it.

Painless harnesses are a HUGE pain. You have to wire the whole thing yourself. They label the wires but there is effectively no harness. You can save a ton of money by just getting rolls of colored wire if you want to do it that way.

Call Bill Evans at 814-864-2622. He makes his own and gets my highest recommendation.

Spoke to Mr Evans two weeks ago at the Mopar Swap in michigan and he does not make a Main Wire Harness. I have replaced all my harnesses except the main ($$$$) with the YO and have had zero issues

The problem your trying to fix is two fold. First, your old wiring has connection and continuity problems. If the car was all stock electrically, a Year One harness might be a good start for a solution, but you still need to deal with the low amperage alternator output at idle issue, the amp gauge issue and the bulkhead connector issues that are inherant with Mopars.

Second, you've added significant additional electrical loads and put in a high-output alternator. You need to be wise when incorporating those add-ons into a well-sorted out "stock" electrical system that has had the above mentioned upgrades performed. They need to draw power from the correct location in your electrical system in order to not cause problems.

You can get away with piece mealing and adding on to the system as you go and hoping for the best, or do it right all in one shot from the ground up.