JBlast

I have a line on a 57 Chieftain Sedan. It is mostly there. No engine, no tranny. I have a 400 block that I will be building to go in it. My main question is this- how do I come to a value on this car. It will be sold at an auction and I intend to bid on it. I just don't want to end up paying too much. Can anyone give me some insight on how to put a value on a car like this?