Lol, It was late '70s when that happened. But you don't forget that sort of thing. It was my '66 Charger, a 383 car. Had the same diameter as the '68 Charger bar I replaced it with as I recall.
BTW, I'm not attributing the bar breaking due to any stress riser or nick. The only thing I wanted to do then was get another in it. Kind of embarrassing driving a car around with that sort of tilt back then.