You just have minor difference's in the "stamping" between those two lower control arms, throughout the years.
That's nothing to be concerned about.
Just the way one was pulled off the LCA assembly line that day in installing everything onto the car, or maybe one was replaced in the life of a 48 year old car.
If you think one has more "wiggle" than the other, some looseness is pretty normal, on old LCA's, but if you feel it's too much, member Jim Lusk has a video on how to "tighten" up the slop in Mopar LCA's.
Do a search.
