I've read several different ways to clean up fadded, fogged and scratched headlights but I think I can offer a faster, easier method. Less than 15 minutes for boh of mine today.
Sorry no before pix, just wasn't thinking that far in advance.

No, it wasn't my Bonneville, but I'm sure the results would be the same.

First, clean headlights thoughly.
Use a good polishing compound, I used Rolite cleaner polisher.
Now the best part.......... take a heat gun or propane torch and very quickly move the heat back and forth over the headlights being VERY carefull not to stay in one spot.
The heat will fuse all the small scratches and cracks together to make a smooth surface again.
This will not remove the yellowing that sometimes comes with age, but it sure cleans up the plastic almost to new condition.

that sounds interesting

If I'm not mistaken, only the 2000+ are plastic...

correct

Possibly so, but my '92 Chev truck has plastic lenses, and the Bonny has plastic corners. One of the corners on the Bonny has some rash on it, that'* my next project.

I think I would first sand/polish it before I do that to remove the yellowing. Probably would look brand new afterwards.

Thats quite a process you came up with. So do you remove the UV layer with the polish and heat the lens itself?
Or are you heating the UV layer as it sits on the lens surface?

Badmttn, I know you're very passionate about this, but please don't go digging for older posts to update them. This one is borderline. Nobody has posted in it for 2 months.