Jim,
I stand corrected.
I did a little checking (over 300 car ads in Hemmings to make sure I spoke correctly) and found that Buick did offer a straight 8 in 1953, but only in a model called the "Super 8". So, we were both right.
It must have been a plain-jane model, that had a standard trans. All the rest I found were with the 322 cu.in. "Nailhead" V-8 beginning with the 53 models. That was also the year the famous "Skylark" was introduced, with that V-8 engine and those neat Kelsey-Hays chrome wire wheels, and a continental spare tire mount on the back.
Frank, Oldsmobile first offered a overhead valve V-8 back in 1949. Pontiac and Chevy came in 1955. Cadillac had a 346 cu.in flathead and a hydra-matic trans back in 1947, but it may have offered that in 1946, I am not sure. I think they changed to overhead valves in 1953 or 54.
A side note here: Chevrolet experimented with an overhead valve V-8 way back in mid 1920's. It was based on the 4 cylinder "Baby Grand" overhead valve engine, (which was the basis for the long lasting 6 cylinder chevy engines to come later). That V-8 never got off the ground and Louis & Gaston Chevrolet kept things going with the 4 cyl. until around 1929 or 30.
Hope you folks enjoyed this info. It was fun writing about it. (Now back to woodworking)
Aloha, Tony