On a 77 hilux with the 20r what's the best way or place to tie into the fuse/holder for a 12V switched source? I found that the 15a engine fuse is switched and can probably use that? I've never really messed with that old style fuse holder before.
Depends on what type of load your planning to use it for. If something simple like to power a relay under the hood I believe the blue wire on the wiper motor is a switched wire. Or grab a test light and probe any open connectors on the harness. If it only shows power with the ignition ‘on’, that would be useable. You need to have a basic understanding how 12V auto circuits are wired. I would avoid any modifications to the fuse block itself.
this is from the FSM i have for the '72 second gen. The fuse box is very similar in a '77. Bottom 3 fuses above the spare are Ign+. You may be able to tap into the lead to those wires from the Ign switch. What exactly are you trying to wire up?