Yes, off road fuel will run in these trucks. The front tank in my IDI was full of it when I bought it. It ran poorly on the front tank due to a rust pin hole on the pickup(sucking air), so it never was used up. It was a farm truck, so someone probably put farm fuel in it at some point.
I always wondered about being inspected. I guess as long as you don't draw attention to yourself, you probably won't be inspected. I'm running blends of used motor oil as fuel, and worried about not paying road tax on it as well... I do blend with gasoline, so I pay some road tax at least and I splash some road diesel in from time to time too.