On my 79 I just cut the two connectors and a foot or so of wire from four light harness on the donor truck. Then just some flat connectors crimped on the ends to that pigtail plug right into the original two light single plug. You do have to do some testing to figure out which wire is which on the plug, but there are only two options. Get the ground right, and try both until you see four lights with the highbeam switch on. Then just wrap up the connection with some tape and enjoy.
I was concerned about the amp draw being higher for four lights in high beam, but I never had a problem with it. I have some wire, relays, and connectors that I was always planning to use to directly tie the headlights to the battery, but it seems the thermal trip circuit breaker on the two headlight LUVs can handle the four bulbs.
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95 Isuzu Trooper Daily Driver
86 Isuzu Trooper reliable backup
77 LUV 2wd stock beltway blaster (resting)
79 4x4 LUV project: 2.6L, 5spd, 31s (eventually)
MEPR: Man, my 4x4 makes all other LUVs look good
