If the engine is seized up then it probably isn't worth salvaging. If it will rotate that's a good sign. Then you can hook a battery to it and at least crank it over and do a compression check on each cylinder. Check the VIN for the engine code to see if its an original 4 bbl car. The 5th digit should be either a Q or an R code if its the 4bbl Cleveland and desirable for collectors so it might be worth something in parts alone, assuming nothing is cracked or otherwise broken.