A case in point was the body type used by 1958 Chevrolets and Pontiacs. This was during the last years of Harley Earl's reign as GM's styling supremo. Normally adept at leading styling trends, by the mid-1950s Earl began losing his touch, running out of new ideas. In part this was because the design evolution of the 1930s and 1940s had run its course, so it wasn't clear to those who had lived through that era what might be done next. In Earl's case, he reverted to the rounded (large radius curves) kind of shapes that he usually preferred. Unfortunately for him and GM, Chrysler Corporation's new slim 1957 line proved hugely popular while making GM car seem bloated and stodgy. So GM launched a crash program to redesign all its cars in a somewhat Chrysler-like manner for the 1959 model year.
The 1958 Pontiacs were styled before Earl and his crew knew what Chrysler had in the works for '57. Production lead-times from concept to showroom in those days ran about three years at best, so nothing much could be done for those Pontiacs aside from fiddling with ornamentation.
Below are examples of the 1958 Pontiac line. Unless otherwise noted, images are of cars for sale.