Like a whole new truck hey?
Excellent Xmas gift, you have a great family.
What I recall about the Dmax, had a LB7, was that the engine will handle pretty much any canned tune no problem (unless you're stacking tunes).
The Allison, while pretty robust, supposedly can't handle lot of extra power in the OD gear(s).
I never learned the hard way what the limit of the trans, but I also never got on it with a big tune in overdrive.
It would hold a "150hp" tune no problem up through 4th gear. Ran it at 90-120hp for 150k miles and the truck ran and shifted as good at 150k as it did new.