The input gears on NP241s are interchangable. There is some difference in the spline cut where mixing and matching can result in some noise generation if the gear cuts are much different. I put a 23 spline into one that had a 32 spline and ran it and it worked fine. I was very happy with my NP241 and particularly the glow range ratio (2.72 -- lowest on the market).
I spent a lot of time/energy mixing and matching different NP241s but only to return back to a completely stock 23 spline passenger side drop NP241D, and wasted a lot of time and money doing it... They are not interchangable really in any way at least between the Dodge and Chevy models OTHER than the input gear. The front half of one case will not bolt to the rear of another, for example. There are also no adapters readily available and it is a chain driven case. It is light though and fairly strong. If it were me I would run a Dana 300 and flip it if need be, also gives you many more options and it is a 2.62 barely noticable difference, with a 4:1 kit also available...