I can say that Lockout hubs from a 79 are NOT bolt on compatible all the way up to 87. While the axle size and spline count is the same, the bolt pattern and diameter of the hub body is different. I tried at one point to swap manual locking hubs from one of my many LUVs onto my 86 Isuzu Trooper and it was a no go. Swapping over the wheel hub also is problematic because the spindle is different in the area of the bearings and seal. You *MIGHT* make it work if you took the spindle, hub, rotors, calipers, upper control arm, and the locking hub from an Isuzu 86-7 or older. The plus of that would be that virtually all of those parts would be an upgrade to the LUV. The problem I've seen though was that most all of the early first gen Isuzu Troopers (84-86 and some 87s) that had those parts also came with auto locking hubs not manual.
On the P'uPs you might find more compatible parts, and many more of them came with manual hubs. I can't say I've had my hands on every year from 81-86 in Isuzu pickups.
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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