I just noticed on the '57 that:

[Philippe COURANT <accf_clb@xxxxxxxxxxxxxxxx>]

Some '57 i saw on factory photos (owner's manual, B&W pics on the
"Imperial photo archive" book) have these "small protusion" but i
never saw a production '57 Imperial with them ! The passenger car
parts list doesn't list them.
Curiously the Imperial on the '57 Prestige Catalog have the
production bumper w/o protusions. .

About hood pad, my '57 had one, the only remaining material  is
under the braces of the hood..

--
Philippe COURANT (Pau, France)
Imperial 57 Crown convertible
Buick 58 Roadmaster sedan

- American Car Club de France (ACCF) : http://www.accf.com

- Chrysler Imperial France : http://www.ifrance.com/c-i-f

- Cadillac " Standard of Excellence " :
http://www.ifrance.com/accf-cad

- SportsCars : http://www.ifrance.com/accf-sprtcar