The 9778 prefix of the number for your "mystery" head indicates it is a '65 head.
And there is a 326-285HP head casting number 22,so it would be my best guess that your "mystery" head is indeed the 326-285HP head.
The extra 8 is probably just to identify it as an 8 cyl. engine,not sure 'bout that though.
Also could be a code to indicate any number of other things.
9778/8/22...
The '65 326-285HP engine is the tempest/lemans 4 bbl. carter carb 10.5 CR.
That would be my best guess as to this.
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