And yet...that is what the NHTSA are doing here, and that's what Congress explicitly directed them to do. They decided to "exempt from section 30112(a) of this [safety regulation] not more than 500 replica motor vehicles per year that are manufactured or imported by a low volume manufacturer" [0] so long as the manufacturer registers correctly for the program, affixes the correct stickers, etc.
Some classic "silhouettes" will just be incompatible with modern safety regulations: perhaps there's no room for a side airbag, or the shape of the grille is more lethal to pedestrians than modern cars are allowed.
[0] https://www.congress.gov/bill/114th-congress/house-bill/2675...