While on the subject of narrow track FSJ axles, I measured my wagoneer front with the ford hubs/rotors and the wheel mount to wheel mount length is exactly 61.25 inches. It seemed when I was researching it I read conflicting numbers anywhere from 60.5 to 63. I don't know what the measurement would be with the 6 lug hubs, but I would guess very similar since the brakes, hubs, and everything line up.
-raymo
4.6 Stroker Scrambler