I used a used relay center out of a Voyager for the relays to run ignition, fuel pump, headlights, and charging system. ... The box I used is very easy to re-wire.
I just finished putting a modern Power Distribution Center in my 65 Dart, but it wasn't easy. It took several weeks of evening work to re-wire it as I needed. I recall it was from a ~95 Grand Cherokee, but could have been a RAM truck. Has 7 standard auto relays in one row (used all), ~10 maxi fuses and ~10 minis fuses. Newer cars like my 2002 T&C have the new mini relays, which helps but the overall PDC is larger and looks like it would be more effort.