Thats one fix. I forget the name of the other. Its like "cross" something. Attaches in the center of the axle and has two mounting point near the shocks. Keeps the handling identical regardless of which direction you are turning, unlike a panhard bar.
Do Not Use A Panhard Bar with the stock type mustang suspension, it won't work. I've tried it, it completely binds the rearend.
Here's the write up on the IRS conversion, but it really isn't necessary for a drift car to use one of these.
https://www.tamparacing.com/forums/f...tick-axle.html