Will work, but require some trimming to the flip kit. The spring perches are higher on the nnbs, so will it bolt up fine. But there will be about a 1/2 gap between your lower saddle and rear end. Triming the top of the top plates on the mcgaughys flip kit that fit into the bottom of your spring perch will make it just like the NBS kits. These cuts will also set the pinion, so trim slightly more off the front.
With that being said, flip kits are not a whole lot, so unless your getting it next to free or a have a chop saw or a torch and a steady hand i wouldn't bother.