The troubles you'll run into are small and annoying but not impossible to overcome. I believe the intake/tb for a crown vic is on the drivers side so you'll need to reuse your top end pieces. The belt accessories and oil pan are likely different as well. The longblock itself should be a direct replacement though. You will want to take note of the flywheel bolt pattern too. Not sure if you're reusing your clutch but it will either have a 6 or 8 bolt pattern. I believe vics had romeo motors though so it likely has a 6 bolt... Hope this helps some