According to this:
http://www.miracerros.com/mustang/t_suspension2.htm
"Shown above is the 3-link rear that Ford put on the 2005 Mustang. It has a panhard bar, two lower control arms, and a single upper control arm attached to the differential case. Note also the new method of mounting the rear sway bar."
Yes, they did something different.
http://bradbarnett.net/mustangs/timeline/05/05/susp.htm
"For 2005, Mustang’s rear suspension has new three-link architecture with a lightweight, tubular Panhard rod that provides precise control of the rear axle. This technology stabilizes the rear axle as the wheels move, particularly during hard cornering."
http://www.mustangheaven.com/2005mustang/index.htm
"Still Rock Solid – Rear Axle with New Three-Link Suspension
Mustang’s characteristic solid-rear axle has evolved continuously over the past 40 years, and the new model takes the car’s signature design into a new dimension.
"We talked to a lot of Mustang owners as we were developing this program," said Hau Thai-Tang, chief engineer. "They are a very passionate group, and a lot of them told us – very strongly – that the all-new Mustang had to have a solid rear axle."
The solid rear axle offers several advantages that play to Mustang’s strengths. It is robust, maintains constant track, toe-in and camber relative to the road surface, and it keeps body roll well under control.
For 2005, Mustang’s rear suspension has a new three-link architecture with a Panhard rod that provides precise control of the rear axle. A central torque control arm is fastened to the upper front end of the differential, while trailing arms are located near each end of the axle.
The lightweight, tubular Panhard rod is parallel to the axle and attached at one end to the body and at the other to the axle. It stabilizes the rear axle side-to-side as the wheels move through jounce and rebound. It also firmly controls the axle during hard cornering. The shocks are located on the outside of the rear structural rails, near the wheels, reducing the lever effect of the axle and allowing more precise, slightly softer tuning of the shock valves."