If it isn't one thing it is something else PLEASE HELP

[kerls72]

I have a very strange situation with my 72 c10 big block.
Truck runs great and is a blast to drive.
But I am very hesitant to drive it anywhere because sometimes it won't start.
I have full power from battery (dash lights work, headlights work and radio works) but truck doesn't turnover of make any noise.
Does the old c10's have something to do with trans not being all the way in park even though it is?
I only ask because yesterday when it would not start in driveway I put it in drive then back in park and it started.
it is so strange happened 2 times in last week and then it will turn over and start with no issue.
I dont remember what I did 2 weeks ago when it started so i can't confirm it has something to do wit transmission.
advice please
kerley