The Super Pak was an appearance only option on Roadrunners and Aspen R/Ts beginning in 77. I had a 77 Aspen R/T Super Pak, it had a 318 2v anda 7-1/4 rear end. In 79 I belonged to the Richard Petty fan club and attended a NASCAR race at Riverside Raceway. It had been raining the morning of the race and the club members along with the local Wing Car club were allowed to drive arround the track to help dry it off. When we were lined up waiting to go onto the track, some guy looks under the rear of my car and tells his buddy "see that there is one of them Dana 60 rear ends under there". Still laughing 30+ years later.
On the F body, the Roadrunner and R/T packages were trim only and could be had with any engine, even the 225.