All Roush Performance Stage IIIs are based on the current SOHC 4.6L GT, which is factory rated at 260 hp at 5,250 rpm and 302 lb-ft of torque at 4,000 rpm. In stock form, the GT coupe distributes approximately 3,250 pounds from front to rear in a 45/55 percent spread.

Load on the SVO cylinder heads, attach the SVO shorty tube headers, and put that supercharger right there in plain sight where it says something. The liquid-to-air intercooler is all but hidden in front of the engine in a very clean, factory-like package. In a program similar to ours, full boost (6 psi) hits the engine at 2,250 rpm, rolls out the best torque (345 lb-ft) at 3,750 rpm, and stays strong all the way to six grand.

Aside from a Roush high-flow air intake and 8.5mm ignition wires, the 281ci engine is bone stock right down to the 9.4:1 compression ratio. Changes to the otherwise stock drivetrain include 3.55:1 ring-and-pinion (3.27:1 stock) on a Trac-Loc differential, a beefed clutch, and a 20-pound aluminum flywheel. Ours has 3.73s and a Centerforce Dual-Friction clutch zinging on the original 30-pound iron flywheel. Theirs makes 315 hp at the wheels; ours has seen 314. The performance figures are also quite similar.

The suspension on RP13 rides better than the stuff on ours because the Roush guys developed them along with the 18-inch rim and tire package. Expensive Roush/Alcon four-piston mono-block (billet) calipers on 14-inch discs collaborate with 13-inchers at the rear. Our car balances 13-inch Baers with 11-inch stockers. Both setups provide demonstratively better braking.


Performance

A 3.77:1 Low gear snaps the ’Stang off the line, and just where the stock engine begins to wheeze, the supercharger is stuffing the big-valve cylinder heads with lots of go-pressure. We hit the 6,000-rpm rev-limiter more than once. Once in Third gear, manifold pressure begins to strut and, real quick, that sucker alongside you is way behind you. The application of grunt is extremely linear, so the car feels like its being pulled by a magnet rather than shot out of a gun. You don’t haze the tires going into Fourth gear, either, because you’ll be too busy booking down the road. Our version feels exactly the same, although to a different blower whine. It’ll break the tires way loose in Low and Second, but that’s probably a function of the heavier flywheel, stiffer gears, and smaller tires (275/40ZR17).


What It Is

So it’s the package that makes the Roush Stage III Mustang, parts that enhance mechanical goodness as well as delight the eye of the beholder. This Mustang is nice eye candy. Not overdone on the cladding, jackboot kinda wheels, and all one color. At roughly $50,000, it ain’t cheap, but if you want the affiliation and perhaps the collectibility, then it might be