340 w/ 727 auto won't turnover

I recently had this. Turned out that the shift linkage on my 727 was slightly out of whack. So, the car thought it was still in gear when the shift lever was in park. I re-set the rooster comb and solved it.

Try starting in Neutral. Try moving the shift lever a bit when starting. Maybe you can find the right position.

May or may not work for you.