From the Junkyard Donor list...
Aluminum Core Support
1978-80 Regal-Century
1978-80 Cutlass
1978-80 Grand Prix-Lemans
Chevrolet did not install on any of their models.
Note: As far as 1971-79 VINS go the 6th character is the year (i.e. 8=1978) on 1980 and newer federal law mandated all manufacturers use a 17 digit format with the 10th character being the year. For example the letter A is used to designate 1980 and B=81 etc. There is no letter O or Q so the year is bumped to the next letter i.e. N=92 P=93 etc with it ending with Y=2000 and again starting with numbers 1=2001 etc.
http://www.turbobuick.com/forums/threads/aluminum-core-support-what-cars-had-them.203568/
http://www.turbobuick.com/forums/threads/aluminum-core-support-q-doesnt-look-hard-to-do.51446/