I guess you would call the wires missing from the firewall connector a minor defect. I doctored my copy of
jimbosprint's diagram, here is an overlay.
They made the wiring diagram for a truck with warning light instrument cluster, and are showing the additional connector with wire colors so you can imagine or deduce how the wiring is for a truck with a gauge instrument cluster (oil, temp, amp gauges instead of warning lights). There are also minor differences in the wiring under the dash for an instrument cluster with warning lights, I don't remember the fine details but it is related to the resistance wire and brown wire for the alternator (gen) warning light. And the instrument cluster with gauges does not have or need the wires that go to the ignition switch for temp light and oil light bulb test during start.