Dear Leif;
I think you got it right.
Chevrolet built the 216 from 1937 through 53 and then the 235 through 1962 model year. The 261 was basicaly the same (but in trucks/buses) and lasted till 1962 also.
I think the (7 main) style began with the 63 model year & went till the Vortec came to be.
Happy trails.