Go to a four link system with long arms. You are right to worry about damage to the housing, doesn't take much to damage it. Reinforce your mounts with axle trusses that will help keep the housing straight. You can get taller coil springs in a suitable length & weight, eliminating the blocks in back. A good set of shocks and correct springs should reduce wheel hop (deep mud will stop it too).
Your bigger motor will still have an effect on the ring gear & pinion, but w/o the loading/unloading it should be easier on both the gears and axles.