If getting a class C or other van-based diesel, be aware that those motors are specifically tuned differently than the trucks.
For instance, my 2006 Express with the 6.6 Duramax is rated at 250 horsepower and 460 foot pounds of torque, while the same motor in the Silverado in the same year was rated at 360 horsepower and 650 foot pounds of torque. Why? Because the engine bays in the vans (both Chevy and Ford) are more cramped and do not allow the same amount of airflow as in the pickups. And since heat is the killer of diesels, without good enough airflow to carry that heat away, the engineers de-tuned the van diesels to make them slightly more tame and to not generate as much heat. That also means they perform at a little lesse level than the trucks.
That is not necessarily a bad thing. As I say, I am quite happy with my van and it does enough to satify my needs. But because of this de-tuning, the vans sometimes last better than the trucks do with some of the notorious Ford failures. The 6.0 liter Powerstroke, specifically. Although the problems and failures of the 6.0 PS in the 2003-2005 models is of legendary status,...those issues were finally determined to have stemmed from not only poorly-designed emmissions controls, but excess heat generated by these powerful motors exacerbated the poor emmissions designs. But Ford vans with 6.0 Powerstrokes have had a MUCH lower occurrance of the issues experienced in the truck model engines. And with Ford having rectified most of those issues for the 2006-2010 engines, the vans of those later years were even less adversely affected.
All this is to say that while there are people who will tell you to avoid the Ford 6.0 Powerstroke vehicles like the plague, that really only applies to the trucks. I was set on getting a Ford E350 with a 6.0 myself when I was van shopping. I just happened to find a Chevy Express with a Duramax at a screaming good price, so I went that route.
The earlier 7.3 Powerstroke Ford vans (1995-2003) are also similarly detuned, but slightly less capable, with only 215 horses and 425 torque. But the motor is legendarily reliable and has an excellent reputation. It was the last of the V8 diesels that can safely be run on biodiesel fuel with a ratio higher than 20% veggie oil,...if that's important to you.
