That's one of the dangers of living in the past. Diesel engines no longer billow smoke like that, in fact, they are, in many cases cleaner then whatever car one might be driving. Today's Diesels have more environmental attachments then imaginable. However, as stated, a diesel conversion is a simple one because diesel is used as a heat source to boil the water to create the steam. Something that I understand is the way they have been doing it in Disney for a number of years now. Whatever conversion is being instituted now, will mostly involve the fact that there probably won't be steam coming out the vents anymore, nor the need for water, but, the whistle is an easy little accessory to add to the train to produce enough steam to operate that. I hate to see them go in a way due to the historic value of the trains, but, I can also understand that the operating costs must be gigantic, just in labor alone.