I dunno brother. . .my 02 silverado had a 12.5" lift on it and I got 38 x 15.5 x16.5, just floating inside the bodyline. I still had to trim a bit for the front air dam (taken from a z71 tahoe).
Thing is, if the tires are too stuffed up in there youre not going to get that nice lifted look youre looking for, and youre going to need an aweful lot of trimming. Plus there wont be any offroading if you decide.
Its still possible, but I would highly discourage it. If you really want 38's, youre better off saving up for a dana 60 conversion, and at least getting some 12" leafs/coilovers.
Tall kits like full throttle, cognito, bulletproof, whiplash, etc.: although they may be sound in their own construction, are all going to do a serious number on your frame and steering components over time. Cracked frame welds are more common than you think, and are not only sneaky and dangerous, but really add up. Trust me, Ive been through it. Just something to think about, speaking from experience.