When these engines were more prevalent, oil pump gears shattering was a common discussion. Sure, they were fine in grandpas Town Car, but the engine was used throughout Ford's lineup and the problem was exposed under high performance applications.
I don't hear any problems about the kevlar belt drive, and these newer engines are seeing a lot more abuse, making far more power and spinning way more rpm than the mod motors were capable of. Additionally, don't ignore the benefit: The belt drive allows the oil pump to be placed in the pan with no priming concerns, no pickup tube/seal problems, and no tensioner/guide issues that would be possible if it was chain drive. And we all know about Ford's luck with timing chain guides and tensioners. I personally trust a kevlar belt over Ford's ability to design a chain/guide/tensioner setup that'll hold up for over the long haul.