On the Chevrolet V8's, the exhaust manifold was the item that was ported, threaded, and the point of Air Injection Reaction. That may be a California Head, I don't know when the "49 states" engines were built with A.I.R. but 1970 seems a little early for it.
1957 Chevrolet 5700 LCF 283 SM420 2 speed rear, 1955 IH 300U T/A, 1978 Corvette 350 auto, 1978 Yamaha DT175, 1999 Harley Davidson Softail Fat Boy
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