Which Bilstein's...
 

'90 Toyota PickUp 4x4 with OME Torsion Bars and Fabtech 2" rear shackles and fitted with 32x11.5r15's. Want to replace current KYB monotube shocks with Bilsteins. Not sure which model to go with either 4600 (0" lift) or 5100 (3" to 4" lift). Truck is a DD with some weekend camping and minor off-roading. TIA!

If you want to run your shocks the right way up take a look at the M95 monotubes from SkyJacker. The rears are a better length than the KYB's. The fronts offered by SkyJacker are 0-2" lift. We have installed the SkyJackers on my Son's 90 4Runner along with some Gabriel monotubes we found for cheap for the front on Rock Auto but they are upside down like the Bilsteins are!