mirror question

[kevmar96]

probably a dumb question but oh well. I have a 72 swb stepside chevy, and i recently ordered a set of replacement mirrors from brothers. When i got the mirrors in and was looking at them they have 3 screw holes for attaching them to the doors and the ones i took off only had 2 mounting screws, as far as i know these were original mirrors. The truck belonged to my grandad then my dad and now me. Also they were mounted under the window but on top of the first body line. I have been looking at some pics and some are mounted in the same position as mine and some are mounted between the first body line and the second body line. When ordering the mirrors they all looked the same but the new mirrors wont mount in the same position as my old ones. I guess after all this my question is are there 2 types of factory mirrors and did i just order the wrong ones. Any help or maybe some pics of yours would be helpful. Will also try to post some pics of my old mirrors and the new ones. Thanks.