I, too, repeatedly park mine in garages with 6' 8" clearance. I've rubbed the roof of the truck on a support in one with less (why they put a speed bump in *just the right* spot for that is beyond me). As far as parking space widths, you might end up with some door dings... our trucks are w-i-d-e. It's not always easy to get them in lil' ol' parking spaces in garages, much less actually get out of the things and not rub your clothes up against the mud and dirt on the sides (or am I the only one who doesn't wash his truck regularly?). All things to consider, no doubt.
I have no lift on my 4x4 (YET) and am running the 265/75/16 Michelins. I'll say this... in Houston, it does affect your parking choices...
HTH.