I don't remember exactly (it's been a few years since mine was converted), but I think it has to do with how it would interact with the crossover steering. I think the 2wd PS lines will bolt right into the 4wd box though.

1986 Pickup extracab longbed "Woody edition"
SAS - 33's, 5.29's, lockright rear.

02 IS300 SportCross - my "DD"
94 2wd v6 extracab
04 Outback Wagon- wife's/family car