The brown wire goes to the positive battery post split ring clamp. It came as part of the positive cable assembly I bought. I don't know if it is technically a fuseable link or not.
BTW, I was told that the battery ground connection that my picture shows on the core support should actually be going to the right fender (for V-8 engines). See Figure 12-8 in the Chassis Electrical section of the 67 Firebird supplement.
