The heads were redesigned in the late '80s after the 603.96 engine was no longer imported to the US but a head from any 3-3.5 liter 603 series diesel made in the early to mid'90s would work (only OM603.97 3.5 liter engines were imported to the US then), but so would a later head on an earlier engine.

There are VERY few used heads with 17+ numbers (partly because there were very few such engines brought to the US - probably many fewer than 10,000 total and partly because some 3-4,000 of the 20,000 OM603.96 engine heads brought to the US in '86-'87 have failed) and good used replacements bring premium prices. Everyone that owns a car with a 603.96 engine (most REALLY like them) has an eye open for a "17+" head at a reasonable price for the day when their head fails!

Marshall Booth