There are two factory tire sizes, depending on how the truck was optioned. The factory tire size also dictates gear ratios and brake size too. Don't trust the door sticker though, most of the 16" wheel trucks still show 225/75-15 as the tire size. If you can get a VIN report from Toyota that shows the options your truck was equipped with, it will show the actual wheel/tire package the truck came with.
They were either: 225/75-15 tires or 265/70-16 tires, either one with matching wheels.
-Charlie
just to clarify, did factory cars that came with 15" wheels have different brakes than factory cars that came with 16" wheels?