The final mods needed to get the Atlas setup running, were new driveshafts. The Atlas inputs and output were about 2" towards the front of the truck, meaning the rear driveshaft needed to "get longer" and front shaft (and spare front) needed to get shorter.
Luckily in the process of going from the OEM rear shaft tube with slip yoke, to an Atlas-required 1410 u-joint on either end and a slip yoke in the rear shaft, the actual 4" shaft tube ended up needing to be shorter, so a local driveshaft shop could re-use the vast majority of the OEM rear driveshaft. For the front shafts, they just shortened the tube and re-welded and balanced.
The last outlier was mounting the front shaft to the Atlas front output. Having taken the front shaft in an out a bunch of times, I really liked the method of bolts into a threaded flange, vs messing around with u-joint straps & bolts, or u-bolts and nuts.. all up in/above the transmission cross member. However some work was needed to be done to get the "Chrysler 1350 CV flange" style to the Atlas "1300 series flange output".
The Dodge transfercase front flange is a somewhat-standard 4" square pattern, with 7/16"-UNF bolts, and a 3.120" register nub. The Atlas front output flange is has dual mounting patterns, one of which is 1/2"-UNC threads also on a 4" square pattern, but only a 2.0" register. So I had to make press-in rings to center the Dodge driveshaft CV assembly to the Alas output flange, and then drill out the holes on the Dodge CV flange to 1/2".
Two for me (installed front shaft, and spare shaft) and two for my friend's matching-ish Dodge...