I’ve tried Back to Black and it didn’t work. This plastic is really smooth.
Anyone successfully gotten these panels to look good again?

Next to rear doors

 

Sand it and paint it and while your at it paint the A and B pillar so it all matches. That is the only way it will match.

 

A very careful once-over with a heat gun can bring it back.
BUT
Like ​​​​​@Icannap1 said, Sanding and painting that along with the A and B will make them match and the A-B probably could use a refreshment after 20+ years.

 

Any idea how it comes off?

 

Perhaps you are thinking of a different model when you say take off the A and B pillars as mine are a welded part of the body on a D1.

 

I dont think we said to take off the A-B, just mask and paint?

The C pillar is attached with some nuts on the inside of the truck that can be accessed through access holes behind the trim.

 

3 nuts per side behind the interior trim. If you remove them put a small amount of caulking around the bolt to seal it so rain doesn't get in and don't overtighten the nuts as the trim is 20 years old and will warp if over tightened.