I'm sitting here wondering what's peaked your interest enough to go down and even look at it...?
Sure, it's an odd teal color, but beyond that? He's already asking for a (in my opinion...)
nonsensical premium for what it is ($20K for what's probably a $15-$17K van), and if you really don't care about the diesel motor being a 7.3L, there's probably another $3K or more premium in that by itself.
If you were looking for a gas van I'd be looking at '05+ (5R110 over 4R100) and be willing to throw an extra $5K at a V10 that's newer, less miles, and a Quigley/Agile conversion...
Just my $0.02, not that anyone asked for it. I would be interested in hearing more about this van if you go down to look at it, or if the owner was willing to compromise on price and it became an acquisition. There is someone up here by me selling an '08 6.0 Quigley for $33K. Think he dropped the price to $28 or so, 100K miles. It's only been for sale for 6+ months. Nice dark green color!
('Up here by me' meaning SF Bay... home for summer).