You don't need to do anything to your Tundra. Just need a quality brake controller (prodigy) and a weight distributing hitch. I like the soft springs and with the WD hitch it rides awesome. I have plenty of power to hold hills at 70 with well over 13K gvw. I get about 12-13 mpg when towing.
I have the same rig you do...'05 Grey DC limited 4X4


'05 Tundra DC Limited 4X4, Nitto 265/70's.
'94 4Runner on Mogs, locked up, Hummer double beadlocks, 40"MTR's, Marlin Ultimate, CTIS, yada, yada...