The bellhousing will swap, provided you have the same style of throwout bearing (internal or external - the front bearing retainers on the transmission case are different.)
The 2WD/4WD issue is a larger problem - the 2WD mainshaft is longer, and can only be replaced with a full overhaul of the gearbox. The input shaft and counteshaft will be the same, as will the central case, so you may be able to keep the thing for spare parts if you have room (I believe the mainshaft gears are also the same, but I won't swear to it just yet...)