I in the same boat as you, except I've already got a HP D44 and I'm setting it up with an Eaton E-Locker, 4.56 gears, and chromo shafts after cutting it down to EB dimensions. I've also got the 31 spline 8.8 for the rear with an Auburn ECTED and 4.56 gears. I'll be running the 4.0L with a manual transmission and 35" M/T MTZ's.
It depends on who you talk with regarding diffs, alot of people wheel their trucks with the TTB D35 and 35's with no problem, while some people swear by the 1/2ton D44's, and some will run nothing but 1ton D60's.
With enough power, you will be able to break anything, and with some respect to the skinny pedal you can also make driveline components last a long time. There are downsides to anything, but if you are willing to do the research then you're more than set to figure out what you need to run based on what you're planning.
There are alot of different opinions when it comes to springs, I personally believe that springs designed for the TTB suspension are too stiff for proper articulation, but I will find this out when I start working on my swap as I will need something holding the truck up until I figure out exactly what I need to order....