It appears this circuit is a direct feed to the ignition switch.
When does it blow?
Got a better look at a service manual. There are 3 60 amp fuses shown. Numbered 8, 13, and 16. Both 8 & 16 feed the alternator. It is a 6 gauge red/blk wire. The #13 fuse feeds the ignition switch. It turns into a 12 gauge or/blk wire as it leaves the switch. Which then feeds the fuse block. This could be ugly :)