Paul.
Don't just put down the shovel, chop it up and bury the bits so that it can never be used again. Unfortunately I reckon it is time to cut your losses and sell whatever you can, for whatever price you can get, then start afresh with a properly inspected car. You are going to lose a fair bit of money, but the alternative could well cost a great deal more. If you had bought a new engine I might offer different advice, but you bought a secondhand engine of unknown condition that you want fit into an extremely secondhand car, either of which may throw up more surprises once it is running.