The 1966 092 heads have a 68cc chamber to make 10.5:1 on a 389, 1.92/1.66 valves.
The 1967 140 2-barrel 326 heads are 62cc to make 9.2:1 compression also with 1.92/1.66 valves.
So it’s pretty clear that someone was using whatever they had on hand, the 326 lost some compression and some performance with the swap to 092 heads.
1963 & 1964 326 heads had the smaller 1.88/1.60 valves, 1965 - 1967 326 heads had the larger 1.92/1.66 valves.
When the intake manifold to head bolt pattern changed in 1965 to the final design all the heads were upgraded to the 1.92/1.66 valves. Previously the only pre-1965 non-SD heads with 1.92/1.66 valves were the 1963 - 1964 9770716 Tri-Power 389, 421 HO and GTO 389 heads.
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1964 Tempest Coupe LS3/4L70E/3.42
1964 Le Mans Convertible 421 HO/TH350/2.56
2002 WS6 Convertible LS1/4L60E/3.23
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