My 1990 Grumman Olson GMC step van with the Cummins BT4 has logged about 2,000 miles so far. It is loud, I wear earplugs while on the freeway, but in the city it's fine. I have some noise killing mat to install to make it better.
It is not a speedy van, with the governor it tops out at 59-60 mph. When loaded with 3K pounds, it takes a 6-7 degree grade at about 40 mph in third. Not a problem with me, as it gets 16 mpg lugging those grades and I'm in no hurry to get where I'm going. When you consider that the van is used primarily for housing, the inconveniences are really minimal.
I plan on finishing my conversion in time for the RTR. Hope to see you all there.