[gpguy]

If this helps the OPs research, I've got an original 78 T/A SE, W72, Y-82, 4 spd black and gold with T-Tops, complete project car(done nothing yet) that I have the PHS for. This is an early 78 build and the accompanying PHS info has a copy of a GM Pontiac Bulletin that describes the "W72 Special Performance Package" and states it has engine and suspension improvements. My car seems to have all the WS6 options (havent checked for those front braces, was unaware of them, thx) so seems like it was rolled into the W72 "Special Performance Package" at least in early 78.