Indentifying 428 CJ heads

The 428 Cobra Jet engine was introduced in mid-1968. It was a revised version of the 427 low-rise head used in 1963-64. All Cobra Jet heads carried the casting number of C8OE. This is an engineering number and the last letter indicates the stage of revision (the higher the letter the later the revision.) All Cobra Jet heads have threaded holes in the exhaust ports for the thermactor emission tubes (although all 428 heads also have these holes from 1968 and later.) If the head has a boss that is not drilled and tapped, it is not a CJ head. CJ heads also have taller  intake ports (about 2 3/8"). No other head made after 1965 have intake ports this large. CJ heads use four bolts per exhaust port for the exhaust manifolds. Intake valves are 2.09" in diameter, compared to the smaller 2.03" diameter in non-Cobra Jet heads.

Source: The Shelby American #51