183410 Panel, with wheelhouse-rear quarter side inner
...according to the GM US parts book in 76 or 77. It was $91.
The dollar went to hell against the deutschmark starting in about 1974-75, and by 1976 just about anything out of Germany was unaffordable on these shores, helping explain why GM started bringing in the Isuzu from Japan and slapping an Opel badge on it. Your 1976-77 parts book shows the panel at $91. My November '73 book has it at $55.50.
Back in about 1974, during the height of the first OPEC oil embargo, I worked for a short time as a "parts interpreter" for Fiat Roosevelt Motors, the US importer for Fiat. My job was to convert replacement parts prices from the lira to dollars, allowing dealers to accurately price the parts they were buying. Anything made with rubber (that derived from oil) would see prices change on an hourly basis.