Alright I been thru it. I purchased a 2001 w/80k last year and went thru the o2 sensors and cat needing to be replaced then I noticed the coolant drop so I looked into it and bought an alabama cylinder head foir around 500 $ shipped, also you need a bolt kit and gasket kit and thats about another $250 at least. and when I took the head off you could see residue right in the middle between cyl. 3-4. There is a dip in the casting there and when I looked at it I said no wonder the Fin things crack the y decided to remove about 1/2" of material in between those valves, its stupid the castin just has a low spot there and its an obvious weak spot.
Long story short get a new head from clearwater or alabama and put it on asap or sell it. I would make dam sure any 2000-2001 i bought didnt already have a cracked head and then replace it with a new one before it cracked. The 2001 4.0's are really nice too other than this head issuses and the pre cats and if you swap it out before it crackes your set!