Doing my best to channel Verne Frantz here
....
There are some parts of the story concerning the 1961 409s that are either misleading or inaccurate. Chevrolet had to cast an entirely new block for the 61 409s since simply boring the old 348 block left the cylinder walls too thin. Camshaft, pushrods, valve springs, and oil pan were all different. And the 409 was available in more body styles than just the new-for-61 Impala SS.