To get redress the party at fault has to be identified. The company you bought the engine from is blaming Ford and presumably vice versa. I have to suggest that you get an independent expert to examine the vehicle and report what the fault actually is. The AA might be able to do this. If not an independent mechanic from another company. Until you have this there is no way you're going to have the evidence to resolve the dispute. Happy to discuss further. I hope hat helps. Please leave a positive rating so that I am credited for my time.