Maybe just California
California has always been the most heavy-handed with this stuff, so it's quite possible. IIRC, the non-California specs dropped to the 305 if you wanted a manual transmission, but the 350 could be had with the automatic. That never made sense to me. I guess shift points and rpm could be better managed with the automatic (a total farce, since the transmissions were easily modified for little cost).
And they were putting in Oldsmobile 403 when they ran out of Pontiac 400 back then
I had a new ‘78 almost waited for a ‘79 but you could only get a 403 when you got an automatic.
I ordered very late in the year.