The valve size is identical. The spring height will be identical. The springs will be identical as will the other valvetrain parts.
The 64 head # 716 naturally is the last year of the early head Intake bolt pattern.
The 65 head # 92 naturally is the first year of the late head Intake bolt pattern.
All of the cast iron heads, EXCEPT for the 421 SD, RA-IV, and 455 HO/SD will flow about the same. RA-III and "Tri-Power heads" are same as stock as far as real flow goes.
A 421 SD, RA-IV, and 455 HO/SD will flow about 220-230 cfm out of the box compared to <200 cfm factory (normal Pontiac) head.
If you are restoring a car, still lots of these heads (716 - 092/093) out there cheap.
Tom Vaught
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"Engineers do stuff for reasons" Tom Vaught
Despite small distractions, there are those who will go Forward, Learning, Sharing Knowledge, Doing what they can to help others move forward.
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