Price range for NOS side exchaust covers

[IH2LOSE]

My brother in law just aquired a set of NOS shark side exchaust covers.GMPART # 1-3972591 and 1-397252 The boxes show there age and the chrome looks like it need's a good polish
I can post some picture tomorow if needed what would be a good price range for these to sell in .Are they still available NOS are they in reproduction?
he is also getting some other parts he has some spinners and caps that are definatly not midyear parts.Did sharks ever have a spinner on caps ?

Thanks for your input