If you don't have the owner's manual, you can likely find a free PDF version online by searching for "1987 Toyota [Truck model, e.g., pickup, 4Runner] owner's manual".
Generally, look in these places for fuse boxes in a 1987 Toyota truck:
* Under the hood: This is the most common location for a main fuse box.
* Under the dash: There might be a smaller fuse box under the dashboard, often near the steering column.
Without knowing the specific model of your 1987 Toyota extended cab (which is crucial!), I cannot give you a precise location. The owner's manual is the only reliable source of that information.