Swap valve covers, Injector/fuel rail, Timing cover, oil pan, Oil filter adapter, throttle body, flex plate (if you are going with an auto) and water pump. Keep the Intake manifold. I did this on my '96 and this is what I needed to do. The new engine should be Romeo, if im not mistaken. I know my '07 crown vic engine was. The '04 should be Romeo also.