Check the length... Those ones that Sheldon referenced are advertised as longer, for use with lowered cars (I think). Seem like 'somewhere' I've seen others being made, but can't remember details. On the subject of the stock 46-48 brackets, like you've shown, I would speculate that it would be easy to locate those. I'm thinking of 46-48 rear ends that I've junked, and the rear ends that I've seen (few) have had those brackets. Early Ford Store, San Dimas, would be at least one place to ask. Or, someone on here, or hamb, surely has one of those rear ends 'out back'. Obviously, opinion.