Yes thats the hole for the plastic wire clip ! I posted a pic for you in the other qestion that show´s the brackets that you ask´s about and you can also see the wire clip in same pic
There is a very good website from a Swedish guy that restored a 1970 R/T A/C 383 Power drumbrake Auto trans car that has a lot of nice preference pic so you maybe can find some good use of those pic !? Weblink is
http://topbanana.se/ but the text is in Swedish thoe the pic have it´s own universal language