This 1958 Pontiac Chieftain rolled off the line during the final season of a nameplate Pontiac had built since 1949, one year before an all-new Catalina made it obsolete. Under its restyled, honeycomb-grille body sat an air suspension and tri-power V8 borrowed from Pontiac’s priciest engineering ideas. Only a few thousand were built this way. Here’s what made the last Chieftain worth a second look.