[LS short box]

As said above Dash pad first.
Mine is a LS swap so layout engine harness (same for sbc or bbc) with the painted cab on. No doors or front sheet metal/box on yet. I ran the front harness down the inside left frame rail to the rad support. Same with the rear harness. It was a Painless harness so the wires were plenty long.
Lot's rubber lined wire clamps to keep everything secure. I hate wiring so I take it slow.
Couple of pics.