Ill find out for you about the shift kit tomorrow since i just had my whole trans rebuilt and upgraded by a Mustang place in my town. I'll ask him what type he put in my car. All I know is torque converter helps a lot too.
I had a Transgo shift kit in my AODE before I swapped to the T56. I liked it a lot, and have pretty much only heard good things about them. It really firmed up the shifts, and made it pretty easy to chirp the tires going into second.(before the h/c/i/sc) As for installing it I am not sure, I had a shop install it for me.