I did it on my 88 PU. I don't remember if the rotors were a larger diameter but, they were thicker. Calipers have bigger pistons than the 4 cyl ones.
It was a bolt on deal. Had to trim the brake backing plates a little for the larger calipers. You also need to get the larger master cylinder (non ABS). What made the most noticeable improvement was going to a dual diaphragm booster.
My brakes went from scary to put you through the windshield with just light pedal pressure. Huge difference. All bolt on.
It cleared my 15 inch wheels but, I had chrome modular steel type. I have another set of steel wheels now with 3.75" backspacing and they still clear.
Plenty of threads on this subject.