Mopar Ralley Wheels - Please explain to me!

Hi folks, new guy here. Big mopar guy but haven't been on the board yet. I'm in the market for a 71/72 dodge demon and knew this was the place to come for various questions I have. First and foremost, can someone explain to me why there is two style mopar ralley wheels? I've heard some are for big bolt patterns and small yet I see both on all year dodges and plymouths. Is it just an issue of centre caps? Pictured is both styles: Thanks all

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