I bought a 5.7 Vortec motor for my sons truck. They hooked it to their oil pump and I watched it spin. It was an ok motor. Read up. you have to hook it to new oil lines, oil cooler, radiator, etc., It gets costly. When we had an issue at about 4 months out, I called them and even though warranty was for 12 months, they said it wasn't anything that they did because if it was going to mess up it would have done it right away but if we wanted to PULL THE MOTOR and bring it back to them they would look at it. If your cores are no good, it gets more expensive also...
If you believe an engine shop should be a clean and tidy place...keep looking, I've seen cleaner junkyards.