anyone hear of 440source.com?

They lie on the heads... this disclaimer here for me is I havent held a set yet. Just going on other's results in terms of flow potential as delivered. You will want to use the 440Source head gaskets as the chambers are too large in one spot and can overhang, causing issues. You will also want to throw out the springs, retainers and locks and upgrade to better ones. I have yet to see OOTB flow numbers or valve springs as supplied that would support 550hp. Great value, but again, with a few caveats.