Ignition Issues - Car Won't Start Intermittently

It first started with what I thought was a linkage issue. My 72 Demon (225 3 on the tree) would intermittently not start while in park. If I shifted into neutral it'd fire right up. I thought my linkage might have loosened up over 30 years of use but figured I'd wait until winter to fix it.

Now it randomly will not start in park or neutral. The first time I start it from neutral it will fire right up but as soon as I shut the car down again and attempt to restart, nothing.

I jacked her up and attempted to adjust the linkage this weekend but there did not appear to be any slack in that connection where the set screw is. I brought up the issue with my Father who is a much older and wiser man than myself. Our two prominent thoughts are either the ignition switch in my steering column or the starter relay.

Has anyone encountered this before and what was the fix? A relay is an easier fix which I might try just to rule that out but I figured someone's had to had this problem before me...

Any help would be greatly appreciated.