Here's a shade tree way to check the lifter surface. Remember, keep them in order!
Take one lifter and hold it horizontal. The bore surface is as flat as you can get, since these are not tapered on the sides.
Touch the base of a suspect lifter to the side of the horizontal lifter, trying to contact the highest edge evenly. It should have a very slight bit of light between each edge while touching in the middle. If not, it could be worn. If there is light in the middle, it's time for new lifters!