OP, there`s no guarantee that all dipstick tubes are indexed into the block 100% accurately....best thing to do is, next time you change your oil, put the required 7 quarts in, let it settle in for 15 or 20 minutes, THEN check your level. Since you *know* for a fact that the proper amount of oil is in the crankcase, wherever the oil level shows on the dipstick is your correct FULL mark. Make a diagram to keep in your glovebox, take a picture of the dipstick, cut a new reference mark on the stick with a small file, whatever.
The road goes ever onward....
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