Like mentioned before, both ORD and NWF make great kits and you will be very happy with both. If you want to keep your doubler 10 or 27 spline, go with NWF (and like mentioned before, their clocking ability is slightly better). And despite what people tell you, if you decide to go with say a 27 spline doubler, you will not kill nuns like the interwebs try to make you believe. My brother has rocked a full 27 spline doubler in his crawler for the last almost 4 years with lots of use, and never had a problem with it (running rockwells, 44" boggers, and now a 383 TBI).
Lately there are lots of other options to consider when it comes to dual transfer cases. Such as ORD's Magnum/205 or NWF's Titan/205, Blackbox/205, or Ecobox/205, and others out there too. The world of putting a reduction box in front of the 205 is getting better and better (from the old Klune V days). And to be honest, I feel like in the long run sets the truck up for better overall gearing options (gets 5.33:1 overall instead of 4:1 like the 203/205 doubler gets you) along with better independent gear options. Most do not run the 203 in low and the 205 in high for fear of breaking the intermediate shaft (which has and does happen if running it this way) and really all you get is a 3 speed with 1:1, 2:1, and 4:1 since the 203 and 205 have similar gear ratios. Since the Magnum/Titan reduction boxes use such a beefer "intermediate" shaft, you have no fear of running the front box in low and 205 in high. Which means now your options increase to a true 4 speed with 1:1, 2:1, 2.72:1, and 5.33:1. Sure they are a bit more money, but in the long run I feel like these are becoming a better option than a traditional 203/205 doubler. Sure, if you have a 203 and a 205 laying around, then do it cause you can save some money. But if all you have is a 205, or neither to start with, I think it's worth going to reduction box route.
Just my $0.02 and informative really
