Lots of stuff changed in the 70s.
The switch from forged to cast cranks, MORE engines equipped with A/C, smog pumps on some cars, etc.
I have a bunch of pullies here from cast crank engines. I have used them on both forged and cast crank engines and had some that fit and aligned better than others. I don't think that a 4 groove pulley is that much different from a cast to a forged application.