Were the bulbs back in the day big power draws? Or was it due to how long the run from fusebox to rear seat sail panels? Or was it for protection from damage? Just wondering why THOSE wires are quite large, yet the tail light harness has much smaller wires.
I think it's just the insulation that is thick on those wires. Probably because they are routed without any additional protection through pillars and roof structures.
I have purchased virtually all new wiring harnesses so that my 15 year investment doesn't burn up. However, I'm thinking those lighting harness and the flat ribbon cable are probably just fine as is. Probably.