You could just mount the drum and wheel to see if it wobbles or if the brake rubs. You can do that without the machine shop tool. You have a new drum so it should be true and unwarped and any irregularity would be an axel hub that is bent. It looks like you have a one piece axel shaft so you...
I am not certain your '79 CJ has Power Brakes. One of my '84 CJ-7s has no Power Brakes, so I am not certain this is your problem. Without listening to it, I would suspect the booster diaphragm if stopping is difficult and possible with great force. However, you did not mention you had any...