have you seen the motor run? I have a 96 LT-1 with over 160K on it and it runs fine, but if they have been abused you might have problems. I would think though with all that is offered, you might expect to around 1k or just a little more. I would not give more than that because with 150k on it, it will need a rebuild (trans too) if you are going to lean on it. You can buy rebuilt LT-1 for 5k or so from some of the crate engine builders, so think about what you might be getting into.
Is it a corvette, camaro or Impala motor? That makes a difference too. The Impala motors have cast iron heads and thus should be a little cheaper.