Welcome to the forum!
Lots of good info here on the site. As far a relays go, I had a problem with the main fuse blowing when I ran the headlights for a long time. The problem was the same as what you’re describing, wires too long with too much voltage drop. I put relays up at the front, close to the lights and ran main power direct from my solenoid to power ’em up and put ground directly to the chassis close to the relay. Original headlight wire used for switching the relays on. No more fried fuses and as a benefit I now have full 14 volts at the dash. Simple to do, well worth the time. There’s quite a few sites that detail this out, just google headlight relay wiring.
Good luck and enjoy your new toy.
Ringo