That's over the torsion bar support/anchors.
Under the car they remove support to lower the chassis.
To get the strength back, they add support inside.
I used the original left side headlight door cover to use for paint matching.
The 88 is painted exactly the same color as it was originally. It was never exactly “Petty Blue”, but very close.
See my thread and pics.
Sorry, it won’t be coming to Michigan.
It was part of the stuff that I bought from a Chrysler Turbine zone rep, back in the 90s.
He was based in MN and took care of the cars in a multiple state area.