Ah, good question.
The 1967 '440' came thru with 10.1-1 Compression, with Flat-Top Pistons.
* Deck Clearance ..... {-.059"} down in the bore.
* Head Gasket ...........{.021"}
The 1967 '440 HP' Cylinder Heads {#2780915} were Closed-Chamber, and came from the
factory at {78 to 80 CC's}. 'NHRA' Minimum CC-level was 73.5
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The 1968 and 1969 '440' also came thru with 10.1-1 Compression, with Flat-Top Pistons.
* Deck Clearance ....... {-.027"} down in the bore.
* Head Gasket ........... {.020"}
The 1968 and 1969 '383 and 440' Cylinder Heads {#2843906} were Open-Chamber, and came
from the factory at {85 to 87 CC's}. 'NHRA' minimum CC-level was 79.5
End Result
Both '440/375 HP' engines had the same compression.
The 1967 '440' had {6.0} less CC's in the Cylinder Head Combustion Chamber, but the
Flat-Top Pistons were {-.032} further down in the Cylinder Bore than the
1968 and 1969 '440' engine.
In '1970'
The Piston Height/Depth was changed.