[DryStout]

I thought this was an intriguing quote from the following link. See below.

http://www.maximum-cars.com/Cars/Car.php?carnumber=624


[Working on a clean sheet of paper, Mustang’s engineering team could have selected any type of setup at the rear, including an independent suspension. So why choose a solid rear axle? The answer lies in Mustang’s position as America’s muscle car.

"We talked to a lot of Mustang owners and racers when we were developing this program," says Thai-Tang. "They are a very passionate group, and a lot of them told us – very strongly – that the all-new Mustang must have a solid rear axle because of its combination of performance and modification flexibility." ]

Who would have thought a solid rear would be chosen over an IRS.

[ESPCamaro]

I agree with Jon.
Why bother with an IRS? You are just going to get a horribly compromised design that probably just won't work.

Want proof that a solid axle works. Tom Ellams CSP Mazda RX3 not only has a SOLID axle but LEAF springs!!
And to call it wickedly fast would be an understatement. And it competes against other cars with IRS, both front and rear wheel drive.

I'll take a solid axle with a 3-link over a junk IRS any day. Hell with a 9" rear, you would probably be able to make it lighter than a production IRS.