You said custom, so that means you are not hard over on originality. Good idea to eliminate boards. Chevy eliminated them too.
Generally speaking, Chevy began this method:
Your new fuse panel is usually placed on the upper left floor board or under driver seat. Your front harness goes thru firewall, over to and across left inner fender, to left headlight. Then crossover on rad support, in a safe manner, to right headlight. You splice at left light to run the right light wires. Also as your harness goes thru firewall, the rear light branch usually goes back under cab and down inside left frame to rear. Use this general scenario to plan what makes sense. As said, the least amount of terminations is best. Every circuit/every wire must be fused.
If your fuse panel is on the right side, then it's the opposite routing. Hopefully you have a modern harness with a nice fuse box for every circuit.
Many folks use a relay. What voltage are you using? 6V or 12V? What harness kit did you buy?
Left is driver side.
