On the bigger trucks (and I would think the pickups too) there are 3 individual harnesses (4?).
The cowl (main ) harness that goes through the firewall from the fuse box on the engine side to the instruments and across the firewall.
The front harness that connects to terminal blocks and goes to the front lights.
The engine harness , as few as 3 wires that comes through a separate hole in the fire wall to the coil, etc.
The rear harness that goes from the main harness to the tail light and frame mounted gas tank.
These connect to the cowl harness with bullet connectors.
So the length of the frame would just require a longer rear harness.
If the pickup harness has the rear harness as 1 piece, just ad your rear harness to the bullet connectors for the tail lights.
