I change my own oil and filter ('05 4.0L), always use 5 quarts. Dipstick says it is full.
I once asked my dealer what an oil change for my truck would cost. He said it was extra capacity and would cost more. I figured he didn't know what he was talking about or was just trying to find a way to overcharge me. He also told me it should use SAE 5W-20 oil (wrong again).
Unless you have some kind of aftermarket sump or oil cooler, your '01 should use 5 quarts.