From what iv'e read and what iv'e heard the Cummins 220 NHH, and the turbo version in this coach are EXTREMELY hard to get parts for. Awesome engines, but really starting to show their age.
They went out of production in like 1973 and although the traditional versions are still kicking around, the parts that are specific to the "pancake" or horizontal versions are getting scarcer and scarcer every year. Cummins no longer supports them.
Like literally no place at all has a water pump, only 1 shop that I know of will rebuild these water pumps and its in San Diego. Same for the fuel pumps, only 1 shop iv'e found to do that and its in Seattle. Im sure there are others but they are few and far between. I was strongly considering another Crown in AZ and that led me to do a bunch of research into these engines, and my search was pretty fruitless.
Not something I want to try dealing with while my wife and kids look on disapprovingly from the shoulder of some backroad in the middle of nowhere. I know that can happen with any engine, but the rarity of parts and support really gives me pause when i'm depending on a 50+ year old engine with many hundreds of thousands of miles on it, for weeks at a time. Maybe i'm overthinking it, but it makes me pretty nervous.
The Detroit 671's in most Crowns are still well supported and parts are readily available throughout the country.
Now if it had an 855 it would be a different story