look at the center of the dash, some old trucks you pulled a 1 foot by 1 foot section of the dash, switches and all out by removing 4 screws to reveal as many fuses as you wish to replace.
I just remember that from when I was a kid helping dad, no idea what trucks those were, but it sounds like it could be yours.
good luck and report back
2001 GMC 6500 Topkick, 22' box, dropped frame, designed to fit into a 9' garage door. 3126 CAT 6spd Man Lo-Pro 19.5's w/ 3.07 rear axle ratio