Why not cook marshmallows on my under dash fire?

Hey that sends me in the right direction. Any idea what the 3 in 1 powers?

Not exactly. Stuff like signals, wipers, radio, and more are hot in run. Brake and dome and more are hot at all times.
They have very few fuses and even less space for labeling on the box. A fuse marked wiper often powers several other items also. Later models had a number by printed by each fuse and corresponding complete details in the owners manual.