Added HP for 2nd carb and header?

[nkaminar]

The header will not do much. The exhaust is pushed out of the cylinders and the stock exhaust manifold is large enough. A high flow muffler might help, especially if you have an aftermarket muffler that is restrictive.

However, the intake side can benefit from increased flow capacity. The air only has the atmospheric pressure to push it in. Adding a second carburetor and a manifold to match will help. This will only be felt at higher rpm. So if you are not going to race your stock engine you will not see much change. The stock engine will not take high rpm for very long. Look for increase of 7 horsepower. See http://www.rarecarrelics.com/tests-t...ord-engine.php.

The best bang for the buck is a higher compression head.