I went to Harbor Freight and bought this stuff in a can called Plasti-dip. It's this liquid plastic stuff that you can either buy in a spray can or what I bought was a can that is open on the top that you can brush this stuff on. Ity is primarily designed for dipping pliers (or any other tools) handles into and it creates plastic grips on it but it also says it insulates against electric shock. On my '84 245 it still has the original engine wiring harness and there were 3 wires at the big grey plug at the firewall that were bare and the wire that connects to the water temp sending unit was as well. I carefully removed the clip that holds the plug to the firewall so it gave me a little more room to work with. I then carefully trimmed the large black sleeve back just enough to find the end of the crumbling insulation. Then I carefully seperated the wires (2 of which were touching) and I scraped all of the loose remaining insulation off of the wires and cleaned them with spray contact cleaner. Then I dipped an acid brush into this stuff (it's kind of thick but that's what you want) and I found that if you pat it on the length of the bare wires it adheres better. The can says to wait 30 minutes between coats and I only had to put 2 coats using this method. They also say that not to use it until it cures after 4 hours but since I not grabbing it (as in pliers handles) then I put it all back together as soon as it felt dry. All told the can was like $8 and I spent about 30 min. doing it. I know that this doesn't compare to replacing with an updated harness but it can help you make that old harness last a little longer. I previously used the spray on type of this product on some crumbling insulation on my drivers door central locking actuator and it's worked perfectly ever since. Just thought I'd pass this on.