Why do 68 & 69 dart iginition switches have different # ground plug ins?

Thanks @Mattax , physically they are different and wont fit, properly anyway. Bezels are different as well.
Del mentioned the light and I know for a fact 68 had that option as I had one before, so electrically this MAY be the difference. Not sure if 69 had this or not.
Go to mymopar.com and download FSM for free, these are a must.
Did you get anywhere figuring out whether '67 switch was different than '68? and whether there was a superceded p/n number?