Buy a pickup harness and splice. There are VERY FEW wires going long. Crimp/solder/weatherpack connectors and sleeve. As you can see, this is what the gurus are saying. It's no big deal. Overthinking.
If you wish, you can "replace" the few rear wires in the new harness with your own longer wires. Use the replaced wires for something else like cab top running lights or whatever extra wiring a flatbed has.
Every
color available, 20 ft spools, $7.
