I met a Ford dealer tech from Pomona Ford at one of the old MATS races in 2006 or maybe 2007 and he said that the 6.0 exploders were horrible motors, they had 176 trucks waiting on their lot for parts under the factory warrantee.
He had attended the IHC training on those motors in the summer of 2003 and was told by all the instructors in that school to not hop those motors up, they were maxed out and would break parts if you even change the air cleaner element to a high flow unit