Dart 72 vs 73 susp dilemma

Nope. Not true. The tie rod diameters were the same for all A-bodies, 9/16". C-bodies ran 11/16" tie rods, and while that used to be a nice way to upgrade the strength it's unnecessary now. The weak part is not the 9/16" tie rod end, it's the spit tube adjuster. Now you can buy tubular adjusters that aren't split, which eliminates the flex in the tie rod adjuster. So you can stay with 9/16" ends
IMO it doesn't make since to pay big $ for tubular adjusters when you can buy new 11/16 adjusters and tie rods for probably less $ and be good to go I always make this upgrade and have for many years