Do you mean taking a rolling shell and having it sandblasted and welding up holes/patching panels and paint?
I'd say a minimum of 5k if you do all the working of tearing it apart and putting it together again. To be safe I'd say 10k, always double your best guess.
I've gotten quotes for sandblasting full cars that are rolling shells (they put it on a rotisserie and take off most of the suspension then put most of it back together) for about 2k in Socal, then paint would be another $1500-2k. That's not including things like weatherstrip, little nuts and bolts, having everything replated or powdercoated and replacing nuts and bolts with matching sets (like a crazy Z addict would) and all the random expenses that projects normally have.