Well, that first bike is definitely of racing background, where mine was just one of the cheaper road bikes available in the late 70s, as my dad bought it in college. That 1976 yellow number looks to be my exact bike. Ironically I just rewrapped my handlebars in creme. Ha.

I'm sure there's some more knowledgeable people than me that can fill in the blanks.

edit: Catalog from 1976. That might help you out a bit.