The 4wd drive hubs are the same for the Monteros, at least, from 1983 to 1991. The Gen II Montero spindle may be different, but I wouldn't know that because I don't have any. However, the only difference in the Gen I Montero parts that mount to the hub are the brake disc for 4-cyl (early) and 4-cyl (late)/V6. You're probably not at risk mixing pickup parts around, but be aware of the disc diameter as the trucks received the larger rotors earlier.

Russell

1987 Raider - Roxy
1988 Mighty Max 2.6L Turbo - Pearl
1997 Mountaineer V8 - Freddy
2000 Excursion V10 - Freya