Differences in timing covers?

You are correct. A 72 cover puts the timing mark on the wrong side and cannot be used with the marks on your 67 damper. Some time in 69 this was changed from driver side like yours to pass side timing mark. Also some covers (i've only seen 68) had bolt on timing tabs. Meaning it was not part of the cover, but a small tab held on by the two lower water pump bolts. How is your cover "shot"? Try placing a want ad here. There is still plenty out there for a reasonable price.