Good call out on the rust; I looked at a clean conversion van for a customer that looked just like the photo ImperialCrown posted.
I'm a fan of the 3.9, but only in the Dakota. Dad had an 89 D100 (yes, they still built the 100 that year) and that engine had to work HARD, especially when he was towing his 19' boat. The original owner of that truck had traded it in within 6 months of purchase because of the disappointing mileage. I think Dad (with his heavy foot) averaged the same 12-13 that he typically got from his V8 trucks. In my 2wd Dakotas (and with my lighter foot) I always averaged 22. Now, I always thought of the 360 as a gas hog (the one I had, in an 83 D250, sure was) but the fact that it wouldn't have to work as hard as a 318 would be the plus here.
A few years back I had an 83 GMC full size van with the 6.2 diesel. Total dog, but no matter how you drove it, no matter how much or how little you had packed in the back, it delivered the same 20 mpg. A decent turbodiesel could have you in the 20s, maybe, but would take major surgery, and of course right now the higher pump prices will eat up the mileage savings. A shame Chrysler never came up with a serious diesel option for these vans, regardless.
