What do you mean by "carb heat"?
I believe he means a heat riser to heat the intake manifold for better vaporization.
If you’re looking for performance, you’re not going to get much from a split exhaust manifold. The issue is the head is too restrictive so a split exhaust is not going to help much.
If you’re going for the wow factor, split exhaust mimicking a corvette style manifold is the way to go. The sound of a split exhaust on a 6 cylinder is pretty sweet too. I too would like to go that route in the future.
