Why not try adding a good package with heads (edelbrock), a cam, intake, and carb. Then see where that gets you? It would be a lot cheaper and easier to install too. Besides if you add a 440source kit then you'll need all these things anyways to get the most out of it.

I have a 440source 512 kit in my 440 and it runs very good. Machinist liked everything when putting it together except for the main bearings. Just stay away from their water pump and housing..