Is this the speaker you got from me? If so, does it sound ok for you?Just an update.
I installed the replacement speaker in the GT tonight - bolt in after all. My old speaker has an adapter on it that attached to the speaker, then the adapter attached to the grille. Not sure of it is original or not, but if it was fabricated, they did a very good job. I can find out as my Dad was the original owner, I'll ask him.