I am pretty sure that the 350hp version had 11.00to1 compression with 2.02 valves and the 300hp had 1.94 valves. The carbs were different the 350hp had a 585 cfm single line holley and the 300hp had an Carter AFB I believe. The cam shaft was different like 68 Chevelle said. It also had an aluminum intake. I got all this out a 67 Chevy manual from the Dealership. If anyone wants to know about 67 Impala's , Chevelles, Camaros, Chevy 2's, Corvettes or Corvairs let me know. The book is a big binder that says Chevrolet finger tip facts on the front. I think it came out of a salesmans office in 1967.
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Malibu 307 (aka 406 smblk)
69 SS 396(aka 454)
Wolf in sheeps skin