The 348 and 409 engines were the same basic engine. The 409 was increased to 427 cubic inches in, I think, 1963 but was not the same engine as the big block engine we know as the "RAT". I believe the 348 was introduced in 1958 or 1959. I don't have my referance materials handy so I'm doing the best I can on these dates!

 

is this 427 you are talking about,the tall deck truck engine,they say aint worth a damn.wasn't the 348 the first big block chevy offered.

 

The 348 was the first larger displacement engine block offered since the small block 265 that was introduced in 1955. The 427, Chevrolet RPO Z-11 I think, was the engine to beat on the drag strip in 1963. This engine was just a larger 409. I think all they did was increase the stroke but as I mentioned my reference materials are not currently available to me. The engine was rated by the factory at 430 HP but was way under rated.