What is the top fuse for in a 1966 mustang?

In a 1966 Mustang, the top fuse (usually the largest amperage fuse in the fuse box) is typically for the ignition system. It protects the ignition coil, distributor, and other related components. However, the exact function *could* vary slightly depending on specific options and wiring configurations of the individual car. It's always best to check your owner's manual (if available) or a wiring diagram specific to your year and model Mustang for definitive confirmation.