A Serial # will get it right, but looking at the cowl, that basic cowl decal was used 1980, 81, 82, 83. The 82 and 83 engines were prop rated, older engines were crank rated
there is a "build date" stamped on tha base of number two cylinder on tha block half.. its kinda right behind tha bend in tha timin' arm.. will be 1/4" numbers.. mo/d/yr..