Why change out the case? Just replace the sidegears and spiders as a SET. You can clearance the cones right away while you got it apart, to ensure years of trouble free operation. I set that to about .080 (not critical) by machining off the bottom of the cones. Then I shim the side gears back toward the center of the case by doubling up the sidegear washers; the sidegears have to have a lil backlash to operate smoothly. So you may need select fit washers. I get mine at the Mustang dealer,lol.
Finally I set the turning torque to, in the range of 110 to 120ftlbs, using the oil and additive ratio that I plan to run,well mixed. A hundred# is not enough and too much more than 120 will make it want to act like a spool with skinny tires.... 120 works well with my baked-hard 295BFGs.
To do that, I do whatever it takes in terms of spring preload. If you do this right, it will be a once in a lifetime deal. Ok, I confess; once in 20 years or 125,000 miles for me and still going.
