Knafel Pontiac had quite a few quick Pontiacs.
They had a '65 GTO record holder.
And this '66 GTO apparently won lots of trophies.
https://www.google.com/search?q=knaf...hrome&ie=UTF-8
Bill Knafel bought Anderson Pontiac, & kept the Anderson name for several years. So, there were some pretty quick Pontiacs with Anderson Pontiac wrote on 'em.
http://www.pontiacpreservationassoci...ll-knafel.html
Many of those 421SD cars were more like factory stock race cars. They used Pontiac factory engines, but the car may not have come from the factory with those engines. In some years, the 421SD parts were available over the counter, but could not be ordered in a new car. Pontiac also installed some of these engines into '63 Tempest bodies, & gave them to selected Pontiac racers.