Again, this is a topic that's been raised frequently on the M100 site. What is not always known, or at least can be confusing, is the type of water pump housing (between pump and engine block) that is fitted to early and late 6.9s.
All later models have the 'standard' housing with the square based water pump. However, early 6.9s had a replica or, really, the same water pump as 6.3s, with a housing that, to all intents and purposes, appeared to be the...