Sorry I guess I'm getting grouchy in my old age..yes you can change these out and retain the same axle housing and 3rd member. the one part you will need to retain from the gen 1 (if a SWB) are the rubber bushings at where the arms connect to the frame. The long wheelbase bushings appear to be the same from gen 1 to gen 2 but I have not confirmed this.

99 Gen 2.5, fixing blown head gasket
89 SWB- 33's, ARB Front locker, SR rear locker/axle, SR F brakes, winch, WST Offroad Armor all Around, 2.85 Aussie T-case Gears (SOLD)
Sold: (2) 95 SR's, 86 SWB, 90LWB, 91 LWB
-Can Change a timing belt in my sleep..