Today on my 86 I removed the front wheel to check brakes and suspension. As we do this time of year. I noticed a bit of loose undercoating and picked it off. Well 40 minutes later 90% of the undercoating is on the garage floor. I could believe how loose it was. A couple hours later the inner wheel well in clean of undercoating. I got lucky as there was not a bit of rust. Paint looks brand new as it hasn't been seen in 29 years.
The panel on the rear on the right side(behind wheel) is cracked and pitted. The front panel is better but rough. I was going to clean the with muriatic acid but I was afraid I'd get back swiss cheese. Anyone know where I can get these? What is behine rear panel behind right front wheel.
Sorry for running on

 

The wheel arch panels each end of the wheelwell are plastic. They are still available on UK ebay at least. Behind the RHS panel is a big wrapped loom that enters this area from the engine bay just below the wing bolt line where the bonnet shuts. Inside is a large connector that goes into a firewall plug and into the cabin. If you remove it you can check out the rust proofing coating, if any, behind it, and also see the state of the sill end, even if you want to, inject some anti-rust into said sill end. Well worth doing as it is the ends that go. When refitting the panel, it is a very good plan to seal all round the edges with gunk, as trapped water ingress is your enemy behind the panel.

If you fit a new panel, be careful to use a short blunt ended screws along to fix it to the metal panels, or you can short out the loom to the ECU. As I found out the hard way.
Greg

 

I have two panels that are metal and one that is plastic. The plastic panel fits below the metal one in front of wheel. The metal panels are really thin.

 

Sorry, brain fade caused by old age and vintage wine. The rear panels are thin metal. Maybe the front ones were too, though the new ones are plastic I think. Does not matter, they are there to protect the cavities from road grit, spray, water, etc.
Greg