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Yes Ford did change from 1/4 to 5/16 control valves in 67. As for 6-19-67date, I do not think there was a hard date for the changeover in the three plants.
The date code is stamped on the cap. Rebuilders mix the parts up so the date stamp becomes meaningless.
Top right picture in my post above is a NOS/service replacement
The important thing is that the hydraulic line style changed maybe around 1974. You can't easily use the later line style on the earlier cars and vice - versa. The cap can be swapped to fix the date issue. Often the attaching screws are changed to a later style allen cap screw head too. The screws on a 1960's era control valve would be a integral washer filister head with a straight slot screw drive.
Mid year 76 change-over (if memory serves).Granadas were still using the control valves trough 1980.