Here are a few 318 dampeners I have on hand. Looks as though they are correct and have not slipped.
'70 and newer 318s with passenger side exit aluminum water pump. Timing mark casting is on the driver's side of the timing chain cover.
'68 - '69 and earlier (red painted blocks) have cast iron water pump that exits on driver's side. So the TDC timing marks are on the passenger side. So that would put the earlier 318's damper TDC slot in a different place on those early years.
Here is a '71 318 dampener:
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And another 318 Dampener.
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Check your crankshaft Keyway in relation to the TDC slot on your dampener.
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