Iveco. The 6-cylinder 120PK version would be great for your purposes. No complicated and potentially troublesome engine electronics to worry about. Much cheaper to buy and maintain than the others you mention and built to last for years.
Just make sure its an automotive based engine - thus lots of widely available inexpensive spares and plenty of engineers with expertise on them. For inexpensive units that are easy to maintain, Ford based engines still take some beating.