I bought from ECS and it came with a metal pad embedded in the windshield! Not the button but a pad that the button attaches to. Totally NOT correct. I paid $450 for the glass and my date code etched into the glass and $300 shipping for a windshield that is not correct. Charlie, the glass guy at ECS, is having a hard time finding glass without the pad. I told him I would not have bought the glass if I knew about the pad. Since they are Mopar guys I asked him if any Mopar glass came with that pad and he said no and I said neither did Ford or Mercury. So be sure to ask about the metal base pad.
Guess your describing a purchase for your 70.
By "pad" do you mean a somewhat small metal pad with a small depression towards one end (centered but more near one end if I recall correctly) ?
If so that is what is commonly found on 70-73 Mustangs and Cougars for the interior mirror. Some related pictures in the thread below
70 Mustang Rearview Mirror
https://www.concoursmustang.com/forum/index.php?topic=28330.msg172992#msg172992
