Yeah, what Kartman said.
The Titans are incredibly picky about offset and backspacing. I am in the same situation as you and so far haven't gotten much closer to an answer, other than narrower is better. Your best bet is to use OEM wheels as they seem to allow the most flexibility in tire sizes. I have heard of folks running some 35x12.50's on OEM wheels and leveling kit without rubbing.
I am going with 18" aftermarket wheels and was told to try and keep a wheel width of 8-8.5" and backspacing of 4-5-5.0 inches, and to use a tire less than 35x12. Wheel and tire options that fit my taste are pretty limited in these sizes. I guess I am just going to have to buy what I think is my best guess and hope it works
