I have read a variety of posts that offer conflicting info. Some said that the 6.2 or 6.5 Duramax is an (almost) direct swap for a small block v8. Is this true? and if so, to what extent? I am looking at options to put into a van to help it get better mileage and have more longevity. I had originally given up on a diesel engine and was looking at putting a V8 into a Chevy Astro AWD when I started reading posts about these two engines being able to mate up with Chevy trannies and having the same engine size. Any help? If purchased new, and taken care of, are they likely to last 300K miles?