if i were in the market, (and i wish i was) i would pay 400 for a steel halfcab and bulkhead that needed work. id pay 550 for a set that was structurally good, but needed finishing, i.e. paint, surface rust cleanup... i wouldn't pay a dime over 700 for a set in great condition. my main reason for saying that is that if i'm willing to spend over 700, then i may as well buy new...
i would love to have a half cab and bulkhead, but i have so many other thing that need to be purchased for my project, that will have to wait a little longer. if its in as good of shape as you say then post a ad in the for sale section w/ pics and mark it 700... just be willing to negotiate if people think its high...