Rick,
Since the '67 was still a 230 I'm not aware of a pressure/gauge change?
Unless you're sure I would confirm it's a 6cyl gauge and not one from a V8.
If you're not sure, post over on in the Firebird section and/or on our OHC 6 Facebook page.
I'm sure others will chime in.
Sorry, I can't help further.
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When I die, I want to go peacefully like my grandfather did, in his sleep.
Not screaming like the passengers in his car. 
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