An 89LWB gearbox is slightly different from a 90-91 Gen 1 gearbox. the main pitman shaft that connects to the pitman arm is a different diameter... 90-91 being a little larger diameter (beefier) also requiring a different part number pitman arm. I believe the ratio's are nearly identical. Otherwise the gearboxes are the same for 89 to 91 for LWB. I have an 87SWB out back, but havent compared it's gearbox yet to either of the LWb sets I have.

89 Montero LS 3.0L/Auto
90 MightyMax 2.4L/Man

Parted/gone - parts available!
89 Montero LS 3.0L/Auto [Blue/Blue] (2 of 2)
89 Conquest SHP
88 Conquest SHP
87 Dodge Raider 2.6L/Auto
91 Montero RS 3.0L/Auto

Others: 37 Lincoln