What should govern what port you choose for what is whether or not it will fit along with your fat little fingers. I'm assuming you're going to put a little shut off valve in the manifold -- they're only a couple of bucks from Summit -- but you have to make sure that you can reach your hand in there and that the handle of the valve doesn't hit something (like your front carb, or in my case a Turkey Pan, which is removed for this shot). Here's the shot of mine and you can see why it is why it is:
