If you got a 70 and later IRS DSC case, the guts from the SSC can be dropped into this case without disassembly. IMO this is the best choice.
The Rhino case uses the early pinion bearing, so to use your SSC parts requires stripping the pinion shaft to change the pinion bearing. The shaft for the reverse idler, the mainshaft needle bearing, and the clutch cross shaft from your SSC will not fit the Rhino case. All these parts would need to be sourced. (extra $)
I think Airspeed has some DSC IRS cores that would do the job. Look for a guided TO bearing. You will also need to get the swing axle parts. Two Mg side covers, diff bearings, spider gears, side gears, spider gear shaft. fulcrum plates, axle tubes, axles, etc.