Sorry I didn't point that out. I have another lengthy thread here on FABO regarding these brackets and their application. I'll hunt that up this evening for you and post a link to it here.
Quite simply, you remove your old 6"x9" early A-body or 4"x10" later A-body original speaker, add a couple of modern two-way speakers to my bracket, and mount it back into the same location using the original mounting screws. Usually, no muss - no fuss (depending upon the chosen speakers).