'68 318 - Coolant left in heads when removed.

68 is on passenger side and can either be molded into the cover or a tab bolted to the cover. 69 moved over to the drivers side.
'69 still has the timing indicator on the passenger side too. Early '68 and older had a bolt-on tab for the timing indicator. Late '68 started the cast-in-cover version which continued through the '69 model year. Starting in the '70 model year, the timing indicator was still cast in the cover, but, moved over to the driver's side.