'66 Heater/AC wiring questions

[Rust-O-Matic]

I'm trying to sort out the heater wiring in my '66. It has factory a/c, but is missing the compressor. I don't care about that at the moment, just need the heater. Looks like most of the wiring in the glovebox area is still there, but I don't think there's power run to any of it. I replaced all of the other cab and front harnesses with factory type replacements earlier this year, and don't recall where or if there were wires running from the fuse box area or front end to the heater. The original wiring was a terrible mess anyway.

So with that said, I'm sitting here studying the diagram and it looks like there's supposed to be a 10ga. gray wire running from the hot terminal on my horn relay, through a fuse, into the 12ga. orange wire that is currently attached to a relay behind the glove box. I have the orange wire but not the fuse or gray wire. Does anyone know what amperage the fuse is supposed to be? And does anybody have a pic of how this gray wire is supposed to be routed to/through the firewall? I wanna keep it stock looking since the other new harnesses look factory.

Next, there's supposed to be a 24ga. black/white wire coming out of the main harness plug where it passes thru the firewall. That runs to a brown wire, through a fuse, and into the fan control switch. Is this the hot lead into the switch? I'm a little unclear on whether the fan is powered by that wire, or the fat orange wire from the relay mentioned above. And what value should this fuse be?