take the kick panels off, and panels along the floor in the rear, pull the carpet up a little untill you see plastic covers that pop off with a screw driver, the top of the bolt will be right there. the front are about in line with middle of seat, and the rear, if extended cab, is pretty much the very corner of the cab.
also if your going to do all this work, i would replace all the body mount bushings, even if they dont look badly worn they probobly are pretty beat if there original. mine didnt seem bad but in replacing them i noticed a tighter feeling in the truck when cornering.
one more thing, spray the penetrating oil for a few days at least, a week if you can before getting at the bolts with a wrench, they suck. bad.