I have zero experience with tractors, but recently purchased a Ford 8n. I decided I should change all of the fluids and that went pretty well except for refilling the engine oil. Everything I have found online says the 8n should take six quarts of oil, yet I am up to seven and a half, and it is just barely registering on the dipstick. Also the engine is knocking slightly more than before I drained the old oil (which was to the full level on the dipstick). I'm fairly certain the dipstick is original to the tractor and seems to be the correct length based on all information I could find.
And yes, I am certain I actually put seven and a half quarts in, and none has drained out.