I have a couple of suggestions;
Depending on how "show car" you're going, some of those if not all those fuse block wires tie directly to the battery, so I would mount it closest to where the battery will be and run the cable through the chassis, or nutsert them along the way attached to the inside of the chassis.
If this truck will not see much as far as bad weather, perhaps relocating the fuse block inside the cavern that is the wiper cowl may work.
Or bring it into the cab in the area where the original ECU was . Once you remove the dash, you may also find more available space where that can be mounted. Preferably somewhere behind the glove box.
Just remember these are fuses and while unlikely that you will blow them, if you do, consider the access to getting to them.
I don't know your timeline, but that is one of the many electrical issues I am tackling as I cut my harnesses and hide all the wiring as well. Once I get going, I will share my journey and hopefully offer inspiration.
