The crankcase holds 5 quarts. Drain the oil and add 5 quarts. After it's had time to sit for a while and settle, pull the dipstick and see where it is. If it's on the full mark, you're fine. If it's not, you probably have the wrong dipstick or dipstick tube.
Just make a new full mark on your dipstick if this is the case.
If you have a canister oil filer, add another quart but that won't change the full mark on the dipstick since the quart of oil will remain in the canister after you start driving the truck.
