Confused on wiring. 1964 Barracuda.

^^There is if I'm seeing what that diagram indicates, IE the map light circuit originally is unfused.^^ Makes you wonder, tho, if it is a misprint. OP does M3 ACTUALLY connect in the box to the unfused buss?

Another thing you could do is clip that wire and add an inline 5A or so fuse to that circuit. (the glove box lamp)