Join Date: Sep 2011
Location: The Hill Country of Central Texas
First, it's not a "4 valve", it's a "4 venturi" as in 4 carburetor venturis or a "4 barrel" as it's commonly called.
C9OE is correct for a '69 Mach 1 with a 351W, both 2V (H) and 4V (M). The O means that the Fairlane/Torino group was responsible for the design work on that block regardless of which body it was going into- Fairlane, Torino, Mustang, Galaxie or whatever.
The Boss 302 block has a C9ZE casting number because the Mustang group designed that block. And the Mustang group designed it because the Mustang and Cougar were the only bodies that engine was ever used in.