I always viewed what the book (or the emission label) gave you for timing as a starting point for timing. Every motor I ever ran across was slightly different then the book or l;able stated when the motor ran its best.

If you have several dipsticks to choose from, change your oil & filter, leaving it down 1 quart, and run the motor to fill the filter. Now, choose a dipstick that shows the oil level at add 1 quart. Then add the quart, and check the dipstick says the oil level is correct.

If you do not have a dip stick that matches the 1 quart low, I would choose the longest dip stick you have, cut the bottom off, and remark it with a punch at the add 1 quart level, and another punch mark after the quart has been added. Gene