Ran the typical 2/600CFM w/ Weiand tunnel on a mild SBC & it was slower... looked awesome. It was over carb/cammed. I like your thinking for aesthetic appeal though... & w/ 390 or even 450's it will be okay. You already know that you will loose low-end, but hopefully gain some high. When your foot is stuffed it, likely you will be over 3500+ anyways.... & it will look awesome on a K-5!!! send pics when done.