wiring harness question

I have a 96 diesel standard cab auto with wiring harness issues. It was used as a plow truck before l bought it and I've been having electrical problems with the head lights woking intermittently, I check the head light switch wiring and noticed several wires with melted insulation so I'm thinking of replacing the dash wiring harness does anyone know which model years years are interchangeable. There are several 2nd generation harnesses on eBay but none specific to a 96. Any info would be much appreciated.