Header brain fart

In about 76 or 77,I bought a used 74Dart-Sport360 4-speed, with headers on it. I mightabin 3rd owner. So I know in Canada, at least, there was such a combo.
But IDK what heads were on mine.And I didn't have it long
I wonder if the difference is just the air-pump holes,under the exhaust ports, which you can plug.