No more smoke except for 5 seconds from a cold start. Everything is good now and it’s got plenty of power. Your 603 sounds like the head is worn out. Does it use oil? Probably worn valves guides in your case.

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Only diesels in this driveway.
2005 E320 CDI 243k Black/Black
2008 Chevy 3500HD Duramax 340k
2004 Chevy 2500HD Duramax 220k