1973 340, want more power.

That one for for driving in cold weather, the air gap version here --> https://www.summitracing.com/parts/edl-7576/overview/make/dodge
If it is a fair weather car and for max power. It's worth a few HP over the standard rpm intake.

A big improvement? In a way, yes, and even more so when the engine gets more and more built up. It's not like adding a two hundred shot of NO2.