I love spending other people's money. My advice "while you're in there" would be to replace the engine harness, as well. The engine harness is less money than the dash harness and a heck of a lot easier to install. I saw some crimped wires in your engine compartment...who knows what other hidden gremlins are in there. Do it right once, and have the peace of mind you currently lack. There could be all kinds of corrosion/shorts inside those wires that can't be seen..JMHO

 

Thanks everyone - I found out that my car originally had backup lights and I've ordered the harness.

Ha -leave it to Leif to make thoughtful, inciteful and intelligent comments. You've convinced me, I'll order up an engine harness for the old girl too.

 

Gary,
If you're not going to be installing back-up lights in place of your current red lamps, I would order the harness that doesn't include that option. If you order the "back-up light" harness you're going to have to butcher it to install the additional two brakes lights whereas if you order the "non back-up light" harness, it will already be wired for four brake lights...something to think about.

 

Thanks Leif, your opinion is always appreciated. Here was my thinking, as feeble as it might be. Since my car was originally equipped with backup lights, I'm assuming that someone wired the two extra tail lights outside of the factory body (rear) harness which I'm not replacing. (Unless you suggest that I replace it too, lol). Before the car died, those extra taillights were currently working with the original back up light harness. I think that if I put in a new without back up lights dash harness, it would be wired factory correct for the four taillights, but differently than what my "extra" taillights are currently wired for. Was that confusing enough?

And - does anyone know the difference between the LL standard harness and the "Service Replacement" harness?

 

The rear lighting harness has the option of Back-up lights and no back-up lights also

Difference Between 1965 Corvette “LL Standard” and “Service Replacement” Harnesses

For a 1965 Corvette, the “LL Standard” and “Service Replacement” engine wiring harnesses differ mainly in fitment requirements, construction, and intended use.

1. “LL Standard” Harness

• This is a factory-correct reproduction made to the original GM blueprints and factory specifications Mid America Motorworks.
  
• It is designed to match the exact wiring layout as when the car left the factory in St. Louis.
  
• It is typically used for minimal to no modification from factory spec, making it ideal for a restoration that aims to keep the electrical system as close to original as possible Classic Industries.
  
• It is often labeled for specific configurations, such as with or without factory A/C, and may be part of a “left re-located” alternator/voltage regulator/horn relay setup CorvetteParts.com+1.
  
• Construction is usually with original-style copper wire in plastic insulation, though some reproductions use more durable materials Zip Corvette.
  

2. “Service Replacement” Harness

• This is a full-assembled, ready-to-install harness that replaces the original factory harness Mid America Motorworks.
  
• It is designed to work with common modifications, especially the relocation of the alternator, voltage regulator, and horn relay from the passenger side to the driver side (common when installing aftermarket A/C) Mid America Motorworks+2.
  
• It is built to be plug-and-play — you don’t need to cut, crimp, or modify wires during installation Mid America Motorworks.
  
• It is often made with more durable materials (e.g., cross-linked polyethylene wire) to resist heat and moisture better than original PVC Zip Corvette.
  
• It is intended for reliability and ease of installation, especially in vehicles that have had electrical modifications or where the original harness is worn out.
  

Key Differences Summary
Feature LL StandardService Replacement
Origin Factory-correct reproductionFull-assembled replacement
Fitment Matches factory spec; may require minor modsDesigned for common mods (e.g., A/C relocation)
Installation May require wiring adjustmentsPlug-and-play, no cutting/crimping
Durability Original-style wire; some reproductions upgradedOften upgraded wire type for heat/moisture resistance
Best Use Restorations aiming for factory accuracyRestorations with modifications or worn-out wiring

Bottom line:
If you want a true factory look and feel with minimal changes, choose the LL Standard. If you’ve already made electrical changes (like moving the alternator to the driver’s side) or want a quick, durable install, the Service Replacement is more practical.