The early 273 from 64 - 68 had no marks on the timing chain cover and a bolt on timing tab... The 318 had the same thing in 67 - 68... The 340 had it in 68...
My 67 273 has the timimg marks on the passenger side. Perhaps it was changed at some point.
In 69 all three had the timing marks cast into the passenger side of the timing chain cover...
Just so you know what to look for...
