The Stovebolt Site Forums The Shop Area The Electrical Bay Ebay wiring harnesses?? Or donor?

My experience is that I mount the box in a good location and run the wires thru a grommet or two on the firewall. The front and the rear bundles go thru the same hole. The rear branch travels down firewall and turns back under and runs along the driver side frame rail. The other bundle travels along the drivers inner fender towards headlights/horn. Some wires go out other small grommets, depending on where the battery and starter are. You will have to look at some trucks in your era to see how original is done to give you an idea. They don't use a firewall connector. You can if you want and mount as a bulkhead connector.
The fuse box has mounting holes. When you bolt it on, you may have to use spacers to give room for the bundle(s) to come out side, top or bottom. Some boxes have the wires coming out the back so that's why it needs spaced off the surface.
I am saying all this with the idea it is mounted to the inside of the firewall above and left of your left foot somewhere. The actual location is your choice but many here have figured that out already on AD. Hope they chime in. Also search this website.