I believe your headlight switch has a fuse already, and a thermal overload.
When you do new automotive wiring, it best that everything is fused or a fusible link used. A fusible linked hot wire to the headlight switch. A fusible linked hot wire to the ignition switch. A fusible linked wire to that part of the fuse block which is always on. A wire from ignition "on" to that part of the fuse panel that you want switched.
Accessory position is the same as Ignition "on". Ignition "on" can be used with motor running or not.
I realize in your case, you have to add a fuse panel. You are doing the right thing. For updating/rewiring a truck in the future, always buy a prewired fuse panel style harness kit. The fuse panel should always be mounted inside cab. This advice is obviously not for the purist and their cloth wire kits.
You are correct, you do not want a fuse panel with separate ins and outs. You want one with two power inputs. Hot bank and switched bank. I'm talking updating older trucks, not hot rods with electronic, bluetooth, computers, etc.
I don't use ammeters, so all my fusible links come directly off the battery or possibly bounce off the horn relay.
A nice bright idiot bulb is easily seen when starting to verify bulb and is easily noticed if a problem arises. Which means I like "3 wire" alternators, 12V and ballast resistors.. A voltmeter will give you gauge feedback if you want that also. It's a simple install in series instead of every hot wire routed to an ammeter, which is used as a terminal block for hot. No good, no how, no reason.
On one truck I did, I bought a donor ATO fuse panel from a newer Chevy truck with all the wires cut. $15. I wanted to do a harness from scratch. I de-terminated all the wires from the panel. Bought wire of various colors. Bought crimp/solder terminals of various types. Bought Packard 56 connectors of various pin-outs, bulb sockets, sleeving and other stuff. I guess it was rewarding or a learning experience. But didn't save enough money to ever do it again.
