A little not well known fact about GM's powerglide trans. The earliest ones had 2 pumps in them. One in front and one in back. You could push start a car equipped with one just like a manual trans. You had to be going around 20 mph
That's how I got my 66 Impala and my 67 Chevelle (before the SB400/TH400 transplant) started a few times!