Since there is a reserve, the real question is "What does the seller think it's worth?"
As far as fair market value, it depends on the market.. obviously the "value" of a truck like that will be higher in areas where they aren't as common.
For the sake of example, a '50 3100 in my neck of the woods that needs a paintjob, but is otherwise solid can expect to fetch between $300 and $800.. the same truck out East would fetch $2500.
The thing with eBay is that your selling products at a national level.. those folks might have a hard time getting $1500 for that truck if they put an add in the local paper, but i'd guess the final auction price on eBay will approach $3,000.
