The flywheels are almost identical. I personally did not have a problem reusing the FMX flywheel. Others may say differently.

Look for an AOD yoke (shorter than C4!!) while you're out and about. You can re-use the stock driveshaft.

You might have to fabricate some mounts as the AOD is tight against the factory mount.

The shifters *are* different for AOD vs FMX (about 5 degrees per detent).Windsor-Fox can help you out there.

Look for a carb kickdown setup from a factory car (Crown Vic '85/'86?).

Happy hunting