It all depends on the condition of the parts. In my part of the country if the posi is good and would run as is $500 could be a going price. Wrecking yards would want $250 for a running short shaft TH400, but they would also provide a guarantee. I can hardly sell one for more than scrap since I'm a private party rather than a business. You didn't mention what year the parts are, things such as what kind of heads come with the engine? Does it have the W/Z exhaust manifolds? If you need these parts for a car here's a chance of getting them all together. You might have to spend several saturdays scrounging wrecking yards before you find a Cutlass/442 driveline for a TH400, if that is what this all came out of. So, all that to say you could be looking at treasure or a lot of headaches. I would certainly have the money in my pocket and get over there to inspect it as quickly as I could, if this is all good stuff it may get snapped up quickly. I tend to be an optimist and hope it's treasure, and maybe half the time it is.
My 2 cents!