the ports on the head are diffent shapes due to the injectors.. but if were just talking bottom ends then there nothing different that will cause a problem..the oil return stub in the block will be threaded but you can change that for the mfi one..(t3 turbo).... ... my fiesta rs turbo was running a s2 block for a couple of years... made a template of a efi block and drilled the mfi block... no probs..