I haven't seen a cheap cummins engine yet, but
http://cgi.ebay.com/ebaymotors/ws/e...9&category=50466&sspagename=WDVW seemed like a good price for the entire package. New or freshly reconditioned, they are usually very expensive - but very efficient. My VW TDI gets 40+ mpg - from an automatic. I had a MB 300SD that pulled 30 mpg - not bad for a big car. My wife's D350 pulls 18 mpg around town - and that thing will pull a house! Diesels are usually ~30% more efficient than gas motors. 35 mpg may be optimistic, especially if you still want some low end power. They make them for marine use as well as bread trucks.