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The aftermarket chases dollars (or the Yuan) and as such makes parts to meet demand.
Currently there is little demand for sheet metal to repair your car as most car owners are asking for parts to fix their 1964, or 1965-'66 Impala (which is but a drop in the bucket compared to owners orders being placed for new sheet metal to rebuild a Chevelle, or a second generation Camaro, or an early model Chevy II).
To meet the demand currently for sheet metal most people trying to restore these cars cut up another Impala parts car that is harder to rebuild (because the front end was knocked off of it by a semi, leaving two pristine quarter panels and trunk parts to salvage and buying another less desirable four door car hit in the back end for front end parts. Between the three cars he owns he may find all of the small parts he is missing as well as having a choice as to other options not found on the project car.
I live out in the weeds so I can have all of the junk cars I want out behind the barn or stored in the barn if valuable enough provided they are not an eyesore or leak fluids. Your situation may vary; but a parts car usually fills the bill.