Google the isuzu engine (ISUZU model NPR ) on line, or go to the local AutoZone (of Pep Boys or your local equivalent) tell them the Isuzu model and get the parts from them, that's the bottom line the previous thread was saying.
I picked the engine number out by looking at the westerbeke link, seeing it was a 126hp engine, and then putting isuzu 126hp diesel parts in the google search bar.
http://www.isuzutruckparts.com/isuzu_parts_specials.htm oughta do it for starters.
I have a westerbeke 30b, which is really 27 hp - not so easy when it's not a truck engine.