Define Scat Pack ....

Scat Pack first appeared for the 1968 model year;

http://www.hamtramck-historical.com/photos-va-7.shtml

More ads that mention it for 1969;

http://www.hamtramck-historical.com/photos-va-3.shtml

The 1970 Scat Pack cars & options;

http://www.hamtramck-historical.com/dealerships/1970DealershipDataBook-07.shtml

That last one was published before the Challenger T/As came out, but they are Scat Pack cars as well.