I have a case I pulled from the donor when my dash melted. It's for RockRanger, but it's been sitting for a few years now. The shipping would probably cost as much, if not more, than you pulling one at the JY. Also have the planataries from a NP231 with the 27 spline input for the 700R4 I kept in case I ever get a ecobox. I sold the NP231 in parts, someone wanted the SYE, someone else wanted the Teraflex 2low conversion.
How long is the doubler? I'm exploring options for way down the road. Want a doubler, but the NWF iBox is still at the top of my list, just because it integrates into my Atlas II, keeping it short. Anything longer, and the transfer case would be trying to use the same place as the floor. I know the iBox would fit, because it and the Atlas II combined is the same length as the NP231 I had under there.
When I'm out on the trails, I always think how nice it would be to have another low range that's higher than my 3.8 Atlas, then combined at roughly 10:1 would be nice for high altitude wheeling when my 4.0 is real gutless. With the 700R4 trans, I will use low range sooner just so I can put the trans in 2nd or 3rd and lock the torque converter. It never gets hot that way.
Your Ranger is one of my all time favorite builds.