The differential for the MTX and ATX are different so you would have to call either Quafie, who makes it, or MazdaComp, who sells it to see if they have one for the ATX. You can also check with Corksport on the MazdaSpeed original replacement one.
The MazdaComp one for the MTX is $1100 plus $100 for a bolt conversion for the half shafts. Basically you will have to remove both half shafts, and the stock differential . Replace it with the aftermarket comvert the ends of the half shaft toa bolt on design and then replace them back in to the car and bolr them to the new differential. I'd do it next week while I'm replacing my shafts, clutch and flywheel but I jusst don't want to spend that kind of money right now. This unit is made by Quafie but only sold through MazdaComp. It's designed to hold upwards of 6-800 hp so there is no real danger of breaking it, you might break the shafts but not the differential.
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