* Sealed Beam Headlights: If your truck has sealed beam headlights, you cannot replace the bulb itself. The entire headlight assembly needs to be replaced. There's no specific bulb number in this case.
* Separate Bulb Headlights (less common): Some 1988 F-150s *might* have had an option for separate bulbs (low and high beam), but this was less common. If this is the case, the bulb type would likely be a 9004 (for high beam) and 9003 (for low beam), but this needs verification by checking your truck's headlight assembly.
To know for sure:
1. Look at your headlights: Sealed beams are a single, usually round, unit. Separate bulb headlights will have a visible cover or lens over a replaceable bulb.
2. Check your owner's manual: If you have the original owner's manual, it will specify the correct bulb type.
3. Consult a parts store: Provide the year, make, and model of your F-150 to an auto parts store (online or in person). They can look up the correct bulb based on your vehicle's VIN or description.
Without physically inspecting your truck's headlights, it's impossible to definitively say which bulb type it uses.
