Thinking about going 5.9

You don't need much cam to wake these magnums up. Stock magnum with a 4bbl and headers said to dyno 320hp so that cam would probably get 1 hp per cid which a decent amount and make an gòod driver.
As for carb I wouldn't worry about it too much. Install a vacuum gauge and if it's pulling way to much vacuum on a full throttle run it Maybe worth moving up for a few hp.