Sorry for the huge diagram! It's extremely basic, but works!
Here is what I have, you will need one FIVE pin relay (still pretty common). 30a should do, but it would be best to post the resistance of your bulb circuits to determine the current draw...That would be both for the relay size and fuse size.
This can look pretty confusing, I'm no electrical engineer, but the noodle in my head says it should work. Now I do not like to run a high and low beam power to a dual filament bulb at the same time for a long period. Which is how your modern car works, if you "flash" your brights the low circuit says energized. If you turn on your high beams the low turns off. I used the painless wiring connectors to the headlights, I'd imagine a parts store would have some basic ones. The high beam circuit needs to have some decent wiring ~12ga (depending on draw) since it will be hitting all four lights on one wire.
Anyway so this is setup to kill power all of the low beam circuits when the highs are kicked on.
I'll try to run through this in a way that can make some sense...
Yellow low beams only
Turn on the stock defroster switch (i do not have a schematic for that, but I have it setup to where you have two wires going to the switch. one ground, and one to the relay)
This grounds out the left control circuit for the relay, switching it.
Power comes from the battery > through the high beam relay > and splits off into the yellow/low relay > power goes out the 87
Low beams, similar to the yellow lows, only the stock low beam wiring controls the relay.
High beams
When the high beams kick on the relay switches power to the low beam circuits to the high beams only (5th pin has power until the relay is switched, killing the low circuits)
this is just how i would do it, I'm no electrical engineer!
