A stock, USA-spec 1980 "should" have a dual vacuum advance distributor. I have seen so much over the years and continue to (such as factory white spokers!!!) that I will preface my posts with "AFAIK" regarding what year came with what, more often than not.
As Steve wrote, it "should" have the fully electronic dual vacuum advance, with main plus a little extra advance. In any case, set the static advance where it runs best under dynamic conditions.