So, Now what about the catalytic converters? They hydro locked your motor with oil..... Which they did! Indicated by the smoke in your exhaust, then a seized motor caused "most likely" by a bent or broken rod. Your cats are probably swimming in oil. And damage to your 02's has probably happened too. You "unfortunately" are dealing with more than just an engine swap. Your issue is, you can't prove anything cause you cant see the oil in your cats, or on your 02's. I hope you thought this through..... I would have tried to settle for money and let them deal with the remains of their mistake.

just my 2 cents.