So IT IS possible to put a 5spd in a Crown Vic...?
You will need to remove the old brake pedal assembly and (more than likely) fabricate a new bracket that holds a clutch and brake pedal assembly from a standard tranny car. (Look in a junk yard for parts that look like they will fit the available space under your dash.)
You will also need to find a manual tranny flywheel for your engine. (Automatics and manuals use different flywheels)
Then you'll have to match tranny mounting brackets (transmission mounts) to make sure the new tranny is properly mounted to the chassis.
The clutch linkage must operate freely without binding or hitting other under hood and under body parts.
The drive shaft may not be the right length as trannys differ in length.
The floor shift mounts will probably need to be modified from some found in a junk yard. (brackets, shifter, boots, seals, linkage, etc.)
Last you have to check the wiring diagram for any tranny mounted sensors that must be altered/disconnected/jumped to allow the ECU to get correct signals.
Lots of work and lots of time. (and lots of trial and error and last, lots of money!)
To be quite honest, it would be less expensive to have the automatic tranny tricked out. There are kits to change torque converter stall points and learning to shift an automatic like a manual, you can get about equal performance. 4th gear in the automatic is about the same ratio as 5th in the stick, so the top speeds would be similar.
All that was told to me in a Best Answer. But here's the question: My '92 CV has a 4.6 liter V8. Would it be just a little easier if I buy another 4.6 liter with a 5spd tranny out of a mustang and using the parts from it, rather than buying just a tranny alone and scavenging parts?