Depends on just how good it is. I'm not sure what the Mustang's using back there, personally, I feel the 4-link is the best setup, but I'm sure some people rather the panhard bar setup, but it don't matter much...Ford hath wrought a damn good LRA setup.
The main advantage to a LRA is the ability to handle lots of torque suddenly without frying CV joints. It's also lighter when properly made, EXTREMELY durable (hence one reason Monster trucks haven't moved to independent suspension, the other that there's no independent Planetary setup) and easier to maintain. It's why the drag racers have held onto it so fervently...They don't seem to know how to make IRS work for them. I think, with the Terminator, Holdiacs, and new Charger, they figured it out somewhat, but a lot of guys running 1000+hp will switch it back to a hugely overbuilt solid rear end. Usually a Ford 9".
On the other hand, there's the road course guys. We won't get into offroad (where I think Independent suspension holds the biggest advantage over solid axles,) but on the road course, the big advantage is on a rough surface. You see, when one tire hits a bump with a LRA setup, it changes the camber angle of both tires, and can also cause the entire axle jump a bit, which makes traction hard to find, even with a limited slip diff. Not to mention, the whole system is unsprung weight, while in an IRS system doesn't have the pumpkin, and the halfshafts and control arms are all partially supported.
However, when dealing with massive power and torque, the CV joints become weak points. Regulations aside, it becomes cheaper with LRA to build an 800+hp tube-frame road or circle-track racer. I'm not saying it's impossible - F1 handled over 1200HP in the '80s, but it's a lot more expensive to develop halfshafts and IRS diffs for road race cars. The other thing is that camber angle on an independently suspended car is dependent on body lean, while LRA systems are independent of the body. I think there's even cambered rear ends nowadays. However, an LRA setup typically has no camber, and it can't be adjusted without removing the entire axle and replacing it. Personally, I think the body lean issue is minimal, since road race cars have so little suspension travel, anyway. It'd only be a disadvantage in an application with lots of lean, like a trophy truck or buggy.
That being said, there are now kits on the market that allow hot rod builders to run IRS setups based around the Ford 9", but they're pricey. Looking one up, it'll run you about $4,500 U.S. complete.
