update on 1979 K10. Everything dead but the lights

[my240]

The truck just quit awhile ago and I started changing everything. After this cold weather I started it yesterday and let it run for 30 minutes , shut it off started it again, etc. Seemed to be fine. Last change was fusible link at starter and thought it did the trick. Today went to garage, turned key, buzzer came on, fan started, dash lights,,went to start and dead. No crank at all. If you shut key completely off and start again, same,,got buzzer,fan,etc but no crank when turning the key to start. I still have headlights so that side must be working but dead when starting. As I said before yesterday seemed fine and today nothing. I,ve changed battery, alternator, starter, fusible link at starter, ignition switch, key cylinder, checked fuses,,,????. Am I looking at a new wire harness? Any ideas would be appreciated.
Thanks