I'd get field level seats and go down to watch him warm up before every game in the bull pen, whcih back then was outside the foul lines next to the seats.
Seeing a baseball go that fast, and the sound it made in the catchers's mitt was amazing. They say he threw 101 mph at his best.
Now they have guy throwing 104 MPH (Chapman) I don't see how a batter can even see the ball crossing he plate.
Bob Feller in his day was reputed to have a 100+ fast ball. Few could hit it but one player, Joe DiMaggio owned him.
I saw him many times a the dome, also. His grunt when he delivered would have been enough to scare me.