Ever seen upper control arms like this.

Ok, what was the plate for? Asking for a friend.
I dunno.
I never figured out a reason for it, in 40 + years, so who knows what some Chrysler engineer, designer, thought of doing that, back in the day.

I've seen them in the past, but very few of them.
So i doubt they were common, even back in the day.

Didn't last but a year, maybe two, so they figured out it didn't do any good, so it came to an end.