If you can get your hands on one, there is an electrical book by year for these vans and it will tell you with certainty. I am still in process of connecting mine as do not have the harness but have the wiring from the harness under the steering wheel to the engine compartment. So I need to splice into that. I did not have the wiring from the harness to the dash. Ford did not include that in mine. You might have it right there.
Something there looks off to me. The wiring is all small gauge for relays and the harness into the switches is smaller if I recall.
Remember, you also have to add relays and maybe fuses to the electrical panel in the engine compartment. The switches inside the cab just trigger relays on that panel for the blunt ends
The wiring diagrams book will show you for sure.