I have a Ford E-350 extended and love it.Everything is pretty heavy-duty on it, but I cannot honestly answer whether or not there is a difference on componets between the 2.I have the 7.3 diesel in my van, and it does pretty well for what it is.I have never had a lack of power being fully loaded.It seems my van is alot heavier empty than most, coming in at 7,500 empty.With a 9,400 gvw, it does not leave much for freight,but alot of the loads I have carried are in the 500# range.The heaviest I have carried is 1,950 and it did wonderful.I totally agree with Greg, get the biggest and longest you can get. As far as where to buy, there are alot of e-350's out there.Pm me and I can give you the name of the person I bought mine from, and she can locate one for you.And there is another dealer in Florida that has hundreds of them, as well, but I cant say enough good about Ryder.The 6.0 ford diesel had it's share of problems,so that is what made my decision to go with the 7.3, which is only available from 2003 and older and has a reputation of a reliable engine with very few problems..But then there is the age requirement to think of as well.It's all what you want.Best of luck to you.