For me, if I can not call the manufacturer or authorized dealer or another parts company and get the parts I need, I consider that obsolete.
I have an old Bus with an 8V71 Detroit, about as obsolete as you can get these days, and almost regulated out of existence in Kalifornia. Ive read horror stories of people out of the road getting screwed over by mechanics who simply had no working knowledge of the engine and didnt want to work on it. At that point it has nothing to do with love or money, you dont even get what you pay for.
I was on a Bus forum and suggested the engine was obsolete and wondered what could possibly replace it, and the response couldn't have been any worse if I had run over their kid on the street and backed up to do it again.
But we both must realize that many never leave port to head off into the wild blue, others have different comfort levels, and still others have enough $$$ they just dont care. Remember too, that new doesnt always mean better. Some of the newer engines are so screwed up due to environmental regulations they are almost impossible to work on without specialized tools and computer software. Finding someone in the middle of nowhere who would know how to work on it could be real difficult, where as an old A4 or mechanically injected diesel would be a piece of cake.
So while your westy isnt exactly current, it was and is a very well made and very durable engine, and canl give as good of service today as it did when new. And unlike a pesky old Detroit two stroke, most anyone will know how to make it run.
I think the bigger point is you have outgrown the current boat, and are ready to move up. Before you waste a bunch of money polishing up an old t, er boat, just sell it as is and look for what you want. In the meantime, research the various engines available in the boats your interested in so you walk in better educated about what you want, as well as what you dont.