Thanks everyone for all the advice. Based on a lot of what was discussed, I turned down the sellers counter-offer. Really good information about Dodge engines for the future. Good info about conversions too. Although I have zero interest in 4X4, I did not think about how that can affect resale.
Maybe the van is ok, but I am not in a position to fly out there to check it out beforehand. I hope someone gets it and it turns out to be really great.
At my budget range it is starting to look like a ground build is in my future.