Call the 428 a family sedan mover if you will. After more than three decades, this big-block remains popular and hard to beat as a source of torque and horsepower. Cobra Jet tune is definitely the way to go. There's also the Super Cobra Jet for overachievers.
Let's back up to April Fool's Day 1968 for the CJ's introduction. Rated conservatively at 335hp at 5,200 rpm, Ford's Cobra Jet put out roughly 375 to 400 gross horses and was hot competition for SS 396s from Chevrolet, 400 HOs from Pontiac, 440 Magnums from Mopar, and literally any musclecar on the street. After a dragstrip test, Hot Rod quickly dubbed the 428 CJ in the Mustang GT "the fastest running pure stock in the history of man."
A high-performance variant of the basic 428, the main features of the CJ were revised heads similar to the Ford 427 Low Riser with bigger ports, a camshaft from the 390 GT engine, a cast-iron copy of the 428 Police Interceptor intake manifold, and a 735 cfm Holley four-barrel carburetor.
For 1968 1/2, all Cobra Jets were coded "R" in the fifth digit of the VIN, and all were ram-air, featuring an air cleaner and flapper assembly mounted underneath the hood. A small scoop admitted cold air to the Holley four-barrel.
Then, in 1969, the base Cobra Jet was coded "Q," while the CJ-R, for Cobra Jet with ram-air, was coded "R." Mustangs (except Shelbys) with "R" code engines came with a Shaker scoop that protruded through a hole in the hood and rocked 'n rolled with the rumbling big-block below. Meanwhile, all other Mercury and Ford 428 CJ-Rs-including the Shelby Mustang-came with an underhood ram-air assembly. The Shaker option was not unique to the 428 Cobra Jet because other Ford V8s used it-the 351, for example-but 428 CJs with the Shaker came only in the Mustang line.
Either the Q code CJ or the R code CJ-R could be made into a Super Cobra Jet (SCJ) with the Drag-Pack option. Drag-Pack Cobra Jets, then, were made with or without ram-air. A common misconception is that 428 SCJs had solid lifters, which is not true. Another common misconception is that R code 428s are SCJs, which is also false.
The 428 SCJs were built with drag-strip duty in mind, which is why Ford beefed the bottom end and added an engine-oil cooler but left the top end alone. SCJs came with hardened-steel cast cranks (regular CJs had nodular-iron cast cranks) and LeMans rods. The assembly was externally balanced with a large vibration damper. The CJ was stock with a nodular-cased 9-inch differential and 31-spline axles.
SCJs did not have a unique engine code, but they were mandatory, with either a 3.91:1 Traction-Lok (code V), or a 4.30:1 Detroit Locker (code W). Therefore, any other rear-axle code on an original data plate proves the 428 was not a factory Super Cobra Jet. It's interesting that Drag Packs with the 4.30:1 Detroit-Locker axle code "W" were referred to in some original literature as "Super Drag Packs," a cool term that did not catch on.