I think Ma Mopar used more Saginaw boxes and that's why you see them more. I have a Federal in mine but I seem to be in the minority. The Saginaw also seems to be easier to modify the pressure output with simple shims. I've not seen an equivalent method for the Federal.

You've got a pile of money invested in the Borgeson box, what's an extra $100 for a pump that is already dialed in for it versus a generic parts store version that you'll probably have to hack into? Seems like you want a drop in solution and it's looking right at you. Take it.