Thanks. Mine looks like this one, except that it lacks the two dimples..
The retainer holds against the axle bearing, which is pressed on the axle. If the axle bearing separates, the axle can still come out... but it is likely you will feel a serious vibration or hear some ungodly noise warning you of this.Yes, they have retainer plates that bolt to the axle housing. One more thing that make a 9" better - if you break an axle, it stays in the car instead of letting the wheel loose to destroy your rear quarter or hurt somebody.
Sounds like you had the same setup that my car has.I also (HAD) a 3.00 open diff. 8"incher in my 73' mustang that was replaced later in life by a nine inch. The best thing about having an 8" rear in a falcon/mustang/cougar is an 8.8 disc brake rear from an Explorer slides right on in!!......of course so does a 9".......The Explorer rear end is about a perfect match to the original width mustang rear as it gets. I have one under my wifes 66' coupe.