Having owned both a 1989 Gen I Montero (Raider) and a 1988 Dodge Ram 50 4x4 pickup (Mighty-Max) I really like your setup!I did it both for aesthetics and to avoid having to carry a spare for the trailer (though it seems unlikely I'd flat an all-terrain on a lightweight trailer). Also because I love the Gen1 Montero wheels. Also so I can rotate around all six since the trailer will NEVER wear these out and eventually I'll have to replace them just because of being too old.
incidentally, no adaptors. my trailer is homebuilt frame with a 3500# trailer axle (built to the length I wanted it to fit the wheels correctly) with 6-lug trailer hubs that fit the wheels.