Dip stick length

Doesn't matter as long as it goes near the bottom. You would put in the proper amount of oil w/filter. Run engine for a few minutes, shut off, wait a few minutes and then install the stick. Pull the stick and mark the level. That is now your full mark. Doesn't matter if it is 4 quarts or 40 quarts.
You wouldn't believe the number of guys that'll put 14 quarts of oil in a smallbock before considering thier aftermarket dipstick may be "slightly" off lol