I appreciate Jay rolling with this, kinda off topic, but fun regardless!
The 68 Mustang race car's, built in Dec, 67 were made so that Ford could go racing with the 428 engine. The 427 engine was expensive for Ford to build, the 428 much less expensive. Ford chose Pomona as the place to introduce it, with each car being given (actually sold very cheaply) to each team. These were really race car's, not an RPO option.
The CJ engine option became RPO in March/April 68.......which is why they are considered 68.5 cars. Yes, 3.91/4.30 gears were available, but not SCJ/Drag Pack.
There were no special engine codes to denote an SCJ apart from CJ in 69. Q code denotes non ram air, R code denotes ram air. As stated, early in the model year 69, the only way to get the SCJ engine, was in conjunction with ordering 3.91/4.30 gears....Mustang, Cougar, Torino,Cyclone. Later in 69 ( Feb, 69) this became known as Drag Pack.
Also remember the oil pan issue which delayed SCJ production until November 68.
428CJ pistons and the 428 Super piston has alway's been a source of confusion. There is no SCJ piston, CJ/SCJ were the same cast aluminum piston made by TRW. The early 428 CJ piston had issues in the pin boss area and would tend to crack. An updated part was released for production in Dec 68 to take care of this which is the piston cast as 428 super.
And yes, in 1970 Drag Pack and Super Drag Pack were available on the 428 Mustang's and Cougar's, as well as on 429 Torino's and Cyclone's.
Brian