I have seen it where some shadetree mechanic has put two right-hand thread ie rod ends on the same rod, and made it so you do have to remove one end of the rod to adjust the length of the rod. It usually happens when someone buys a "kit" that only comes with the outer ends, and the rod is reversed for some reason. I've seen it a few times. I'm not saying that this is what was going on on your car, but it doesn't always work when you loosen both ends and turn the rod. Sometimes it moves closer to one, and farther from the other.
As far as this 70 Dart, are you planning to convert to big bolt pattern? If you are, I'd do it all at once. Stronger spindles, stronger ad cheaper ball joints, better brakes, etc. I'd hate to throw all that money at the small crap if you're going to pull it back off eventually.