Depends on your needs. If you already have the built engine, Trans and now transfer case, SAS on a Dmax will run 7-10K to do correctly. By that I mean, making sure abs
, brakes,ect all work correctly, with not dash lights ect. Yes, it can be done cheaper, not what I call correct.
That being said, as you mentioned, Superduty already has the stronger axles and transfer case. Trans is about even with the allison(My opinion, yes, Ive had both) but to make the HP you have now will be expensive as the 6.0 while it responds well to mods, it usually does not make the same power as a Dmax.
Now, I personally have been a chevy guy my whole life(I'll be 40 in 2 weeks), have had chevy 6.2, 6.5's, and several Dmax's(02, 07, and 11) and while the engine/trans have been GREAT, the rest of the trucks are NOT heavy duty enough..... tranfer case, IFS
, steering, hubs, I dare say even frames......... I was tired of it. Traded in my 2011 and bought an 06 F350 last November, and honestly love it...... I hate it says Ford on the front, but it is a great truck. I have owned/built enough vehicles to know THEY ALL BREAK, but when comparing what the 6.0 was going to need to make a bulletproof truck i bought it over another chevy.
Sorry for the long winded post, and this is just my $.02.... take it with a grain of salt and do what's best for you at this time. Not saying you may not have some issues with the KR, but looks like most of the "6.0 problems" have been addressed with that particular truck