I recently installed a newer transmission into my Mark VIII. The old transmission started to fail due to the worn out torque converter, and typical forward clutch seal rings on the stator support. This time, I wanted to install a newer model tranny, with the factory updated parts such as the mechanical diode.
My old transmission out of the car

Here is a list of what my new tranny has inside:
-Shorter Reverse Servo: E0AZ-7D189-AVMR
-2.7" OD Servo: F75Z-7H188-AA
-OD Servo return spring: F2VY-7F201-A
-Top 1-2 Accumulator Spring: F75Z-7F284-BA
-Pressure Control Solenoid (EPC): XL3Z-7G383-AA
-1-2 accumulator piston: F7AZ-7F251-AA
-1-2 accumulator cover: F4AZ-7F247-A
-2-3 accumulator piston: F7AZ-7H292-BA (AA) (AB)

I also installed a new Torque Converter. I bought a torque converter for a 2003 Mustang Mach 1, as it is fully furnaced braised and has the updated piston. It is the best factory torque converter money can buy

There were only a few things that I needed to swap/replace in order to get this new tranny into my 94. One item to watch out for when doing these swaps is the shift linkage manual lever on the side of the transmission. Many transmissions use a different shift lever, depending on the vehicle the tranny came with. In my case, the Mustang uses a different shift lever than a Mark VIII.

To swap your shift lever, or MANUAL LEVER from your tranny to the new one, both tranny's have to have the pan removed. This is alot easier on a bench, with the transmission up-side-down remove the pan. Just inside the shifter rod there is a large nut holding it in. You have to loosen this nut. You might have to wedge a pry-bar inside the shifter linkage to prevent it from rotating while you loosen the nut. Once you break it loose, you can turn it by hand. Before you remove the nut completely, there is a small roll pin that is just inside the transmission case. walk this roll-pin out with a pair of wire cutters.

Remove the nut, slide the linkage rod out, and remove the manual lever. Do the same thing on your new transmission, and install your old lever onto the new tranny.
MANUAL LEVER

The other item to address carefully is the EGR tube. It is almost snug against one of the transmission bell-housing bolts. If you have to remove the EGR tube from the catalytic converter, be sure to soak it with PB Blaster first, or some brand of spray-on penetrant.
EGR Tube

That is about it. Feel free to email me if you have any questions about this swap. Visit:
www.TCCOA.com for more technical links and information about the JMOD and other 4R70W information. Enjoy the ride!