I have a old Hot Rod mag, which they claim they got 9 hp more by swapping a LD 340 from a LD4B intake. They were happy but I would not be, to much work and $$$ for just a 9hp gain.
That is more so just to show the difference between the 2 intakes and show what the correct intake will do for you. If you were to purchase an intake, and not have one to start with, like a 2bbl. to 4bbl. swap, that article would point you in the right direction.
Having the LD4B intake allready, I wouldn't swap out intakes unless your looking to make some good street power over just a simple upgrade by compare.
They, the mag, was more so happy at the gain, not the amount, by the right intake on the right engine.