The shifter housing on a T56 sits about 2 and a half to three inches farther back than it does on a T45. I am pretty sure you can get away with not building one of those awful shifter boxes. Also, I talked to that kid a few times, hes really nice, but I found a way to do it so that you dont have to extend the wiring harness. There is a spot under the dash that if you pull the harness through the firewall a little farther (without ripping anything, that you can tuck the ECM into. I converted my crown vic to a stick like this. I got my hands on a mustang 5.0 clutch pedal assembly. I grinded down the factory spot welds on the tube that the clutch pedal slides through, and hammered the clutch pedal tube out of the brake pedal bracket. Then I welded the clutch to the front of the crown victoria factory pedal bracket, and slid the clutch pedal in with a billet quadrant. I cut a hole in the firewall, and ran a stock mustang clutch cable underneath to a mustang clutch fork, and voi la. I am in the proecess of doing the same thing to my 95 mark viii. The computer is out of the way now, and there is room for the clutch pedal. I wont have to clearance my shocktowers for the master cylinder either, since the hole is on the other side of the brake pedal for the clutch cable. There is plenty of room in that area with nothing vital in the way for the hole for the clutch cable.
P.S. Hey Edrea, I dont know if you remember me, but a couple of years back, I met you at Bithlo with my 02 crown victoria sport, around the time you were graduating from embry riddle. I remembere tearing you up pretty good. Haha, but now look, you actually inspired me to get a mark viii. I got a 95 pearlescent white LSC. I tried getting a hold of you a few times after that to see if you wanted to go out to the track, but I assume you must have moved back home