IIRC, Logan's Run had some nudity cut to get to a PG rating.
Dark Helmet dropped the F bomb in Spaceballs. (1987) I had heard somewhere if it was uttered twice in a film that bumped it up to a R in the pre PG-13 era.
Then there's the old story Spielberg had profanity in E.T. just to avoid the G rating.
Funny how when Episode III came out, there wasn't much of a fuss over it's PG-13 rating.