If you look in the Bentley you will see that a crack between the valves is
relatively normal and has a tolerance which I believe is specified in the
Bentley.  So if your crack is bigger than spec, you need to replace the head.
 Also I always have my heads pressure tested before reinstalling them.  This
prevents you reinstalling a head that has a leak between the combustion
chamber and the coolant jacket.  Have this done at your local machine shop.

If you heads need to be replaced I would recommend a new head.  I have these
for $395.  You don't have to worry about paying for shipping on your rebuilt
head and core.  You don't have to worry about your core being "bad" and not
getting your core money back.  The new ones are made out of a different alloy
than the original which is supposed to be more resistant to corrosion.  Hope
this helps.

Ken Wilford
Van-Again
John 3:16
http://www.vanagain.com
Office: (856)-765-1583
Fax: (856)-327-2242