How do I install a 5 speed mustang trans in my 97 towncar

In addition to the above you would have to rig up the clutch pedal system and the hydraulics. I suspect you would have to fabricate a transmission mount etc, etc, etc.

I know it's got a mod 4.6 I guess all mustang parts will fit mymyb 97 towncar put hole in floorpan

I would also be looking at swapping out the third member for a lower gear ratio as you will be losing the benefit of the torque converter. A heavy car and high gear ratio may not work well with a clutch.