To give a good answer on what you need to do we need to know what you're working with already. What all can you tell us about this 318? You said it's partially torn down but that could mean a lot of things. It it torn Down to the short block or are the heads and everything still on it? If the long block is still intact you should compression test it. What year is the engine? What kind of mileage does it have? If you have to dig into the bottom end then things can get expensive. Boring it out and putting new Pistons in isn't cheap. The new pistons won't weigh what the old ones did so a balance job wouldn't be a bad idea either, also not cheap.