1987 Ford F350 no headlights or running lights and fuses good on 1990 Ford F-350

1987 not 1990

Asked by for the 1990 Ford F-350
You would need to start tracing a wiring diagram to see if it the light switch or where the problem is. There is a company that independent auto repair shops get their information from, this same information is available inexpensively for people that work on their own cars.. The information is year make and model specific, covering repair procedures, torque specifications, fluid capacities and specifications, service bulletins, component locations, wiring diagrams ect.... Alldata is very easy to navigate