The blunt-cut wires you are asking about are for the PTO and elevated idled. So it you wanted to add an engine-driven air compressor, or utilize high-idle for faster battery charging or using the chassis A/C while parked, these are the wires you'd connect. They also contain the pass-through wires for the factory up-fitter switches, but most RVs re-purpose that knock-out panel for their own switch panel.
There is also a pass-through harness. This is near the blunt-cut wires and has a 4-pin connector. You can cut the connector off, or buy an "aftermarket up fitter" pigtail from Ford. This pass-through connector goes to the rectangle plug near the steering column inside the van.
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