From Alan Colvin's "Chevrolet by the Numbers" (multiple years), 1.94 valves were used on the following "Double Hump" heads (Casting numbers 3782461, 3782461X, 3890462, 3917291 and 3927186):
1962 - 1970 Full size 300 HP (see notes 1 and 2 below)
1962 - 1963 Corvette 300, 340 and 360 HP
1964 - 1970 Corvette 300 HP (see note 1 below)
1964 - 1970 Chevelle 300 HP (see notes 1 and 2 below)
1965 - 1969 Full size 250 HP (see note 2 below)
1965 Chevelle 250 HP
1965 Corvette 250 HP
1965 Nova 250
1966 - 1968 Full size, Chevelle and Nova 275 HP
1967 - 1968 Camaro 275 and 295 HP
1968 Nova 295 HP
1969 Camaro and Nova 300 HP (see notes 1 and 2 below)
1970 Nova 300 HP (see note 1 below)
1970 Camaro 300 HP (see note 1 below)
Note 1: The 1969 and 1970 300 HP engines used either the 3927186 heads with the "Double Hump" casting symbol or the 3947041 heads with the "Triangular" casting symbol
Note 2: 1.94 valves were also used on the 1969 250 and 255 HP engines, but had the 3932441 "Rectangular" casting symbol heads
Also note that 1.94 valves continued to be used into the new millennia, but the "Double Hump" casting symbol ended in 1970.
Ed