A Pontiac 400 in a chevy? I'd pay money just to see a picture of that
Someday I'm going to run a Pontiac engine in a 69 Camaro just to tick people off
I'm getting the impression that you're more into just having it sound good as opposed to actually making a lot more power (there's a vast difference in cost between the two). If that's the case, pick a cam that has a tight lobe separation angle (110 degrees or less) and around 230 degrees duration at .050 lift. If you go too extreme on the duration it'll kill the vacuum (and your power brakes along with it).