Exhibit A: Michael W's artistic photo taken next to the Dixie Gas House around 1971.
Exhibit B: 1941 Pontiac page from Tad Burness' book, "Monstrous American Car Spotter's Guide 1920-1980."
Method: Note how much fender is outside the headlight in the large photo. The 1940 Pontiac line had a completely different and even older-styled fender. The 1942-1945 Pontiacs positioned the headlights at the outside edge of the fender. The later Pontiacs were even more different and lacked the horizontal chrome strip running horizontally along the side of the hood.
Conclusion: Dick and Jeff's Pontiac in the picture was manufactured for the 1941 model year.
Addendum: Note that each of these cars is called a "Torpedo." I did find the phrase "Silver Streak" at the top of another Pontiac page, but not attached to any specific model. So perhaps it's an unofficial moniker for all Pontiacs.