Probably 6-7 quarts with a filter change, but it depends on the filter used. There are standard and high capacity filters for the 454 and the high capacity filter hold one quart and the ulltra high one two quarts.
Isn't the dip stick marked? Change the filter, put in five quarts and start it up, then run it for 30-60 seconds. Then add oil until the dipstick shows "full". Next time you will know how much it takes.
The info in the Workhorse Guide will be correct for later model 454's and probably yours as well, but there are a couple different oil pans used with 454's and that changes the oil quantity. Don't be alarmed if yours actaully takes more or less.
2004 American Tradition; 2014 Buick LaCRosse
Homebase in the Ocala Nat'l Forest near Ocala, FL