As usual I'm with Marine-OpLaw. 5 Quarts with a filter change. I have the Haynes manual that shows 6 also. And if I'm not mistaken so does Chiltons.
The first oil change I did on mine I used 6. Man, it is scary to pull that dip stick and see that you're a full quart over full. You're just waiting to hear the seals blow. That didn't happen of course, it would probably take more oil than that.
I remember this coming up when I was younger. My Chiltons said 6, the owners manual said 5. Guy who worked on my Jeep when I was too scared to do it myself said he put in about 5.2 quarts with a filter and that put it dead on the "full mark" on the dipstick.
I put 5 quarts plus in but not 6. I use the larger filter J trucks call for. Some books oil filter application books call for the larger one but most call for the smaller one. Larger filter obviously means more oil needed to hit full mark.