I too was a service tech for over 30 years, but I work mostly on commercial HVAC equipment. Most of the equipment that I work on, were large box car HVAC units from 50 to 200 ton units. And a lot of my building had the old 50-100 ton Chrysler air temp condensers, and 150 ton to 400 large trane and carrier chillers, all built in the 60's and 70's. The heating equipment I work on, was from small boiler to large boilers, up to 24 ft long. When I was in the air force, I work all over the world. But I still don't like working in tight spaces.

 

Same here but a Ford master tech
I only consider replacing a harness if the wires have corrosion in the copper under the insulation
Green or white Sulphur corrosion
The older the wire the better for repair
The new harnesses I see for Mustangs are made of the new cheap wire and often have problems
New harness at a last resort