Did the '69 verts not have these on the firewall? I know that is where the '68's are. I've seen a few of them mounted there.

The one in my pic is an auto reset circuit breaker. If it sees more than 30A it will trip, and automatically reset in a few minutes. I have a slightly larger 50 Amp one on my boat's minkota electric trolling motor.

The problem I see with running that metal pin in the fuse box and a breaker on the firewall would be if there was a short, it would trip the auto reset breaker, then it will reset and trip again, and reset, etc. To get it to stop you would have to pull the pin out of the fuse box, or disconnect the battery. Where as if there was a fuse there, it would blow the fuse once then you could trouble shoot it later.