Not positive having never done this, but I do know the pedal position sensor provides feedback to the PCM, so if the PCM doesn't see the expected input, it's go into limp mode at the very least.
With the introduction of DBW, the PCMs changed position and went from 1 plug to 3, so I think it would be a wiring disaster to try to install a pre-DBW PCM into a DBW car.
EDIT* Upon further reflection, I suppose you could adapt the Pedal Position Sensor to a an '04 pedal assembly and keep the current PCM, but this sounds like a lot of ifs for little gain.
Edited by RF_Overlord (05/05/21 02:53 PM)
'03 Mercury Marauder (The Blackbird)
Trilogy Motorsports supercharged #61
Too many mods to list / Driveway Queen
'04 Grand Marquis LS Limited Edition (Spruce Green)
Daily Driver (Thanks, Adam!)
'00 Grand Marquis GS (Silver)
Rotted frame and broken transmission crossmember