According to Ford TSB 06-24-4, some 2003-’07
vehicles equipped with a 6.0L engine may require the cylinder head to
be replaced, while design changes can affect interchangeability between
model years and service of 2003-’07 6.0L engines.

According to the bulletin, the manufacturer for this engine used two
separate facilities. And while both locations built engines with the
same design data, three cylinder head variations have been used. There
are engine serial number change dates to help in determining which
cylinder heads were used (see Charts 1 and 2).

The cylinder head gasket and locating dowels also changed in the 2006
model year to accommodate the increase in the dowel size from 18 mm to
20 mm. Using the wrong head gasket for the application will lead to
engine damage  (see Figure 1).

The revised dowel hole was made to accommodate the larger head bolts
to be used in the new 6.4L diesel engine and was commonized for
manufacturing purposes. The injector clamp design and associated
cylinder head casting support area also were modified on the changeover
date in early 2006.

The cylinder head and block dowel hole sizes must be measured to
determine the correct cylinder head gasket kit to be used. If there is
a difference in dowel hole size between the head and block, a special
“stepped dowel” (P/N 6C3Z-6B041-B) is available to accommodate proper
assembly.

Ford notes that the cylinder head gasket and injector clamp versions
are not interchangeable; they must be used with the corresponding
cylinder head versions. Refer to the chart to determine the correct
application.

– From Ford Motor Co. and Ford Truck Enthusiasts (www.ford-trucks.com)