The rest of the story is the engine was basically a stock rebuilt high compression 340 with stock spec cam and 1.88 360 heads. And it had 318 exhaust manifolds on it. And made more than 20hp difference at 3000 rpm- AT THE WHEELS.
Under those conditions the manifold swap made a huge difference, and did not have the benefit or cam or headers to do so.
Point is swap the cam to anything bigger and put headers and good exhaust on that engine, and THEN swap the intake and watch the power numbers go up substantially because the old intake then becomes the restriction.
As always it is using the right combination of parts to get the biggest change in output.
That is $400 well spent for an intake swap, especially considering you could likely sell the old intake for 150 to 200.