The 12G1316 heads were used in the US on Sprites in 68 and 69. Midgets from 68 to 74 and on Austin Americas from 68 to ~70 or so when they stopped importing them.
The early (68 to ~71) 12G1316's have the same port shapes as the 12G940. A bit better in the long radius of the exhaust port.
HTH,
Mike