Cold Air Kit

Have you had experience with cold air kit for a early A bodies? I heard that they can be good for a easy 20hp increase, is this true
Look man, step up and get real. Stop talking in riddles.
1....You have mentioned, variously, early A bodies, a 66, a 68, and a 74. WE have no idea WTF you are dealing with "actually." And you have never mentioned what engine/ carb(s) or EFI combination you are working on. For all I know you've swapped a Maserati V6 into something...................
2...There is and never was such a thing as a "cold air kit" for A bodies. Unlike B bodies (air grabber, Coyote duster) there never was a factory active hook scoop "kit" or option

So what are you working on?

What do you have in mind? There are only a few ways to accomplish "cold air" and NONE of them are a "kit."

1....Install various hood scoops and review such as OldManMopar used to have on his now RIP duster where a bonnet sealed the carb to the scoop

2....Radically modify the cowl to use it as an air box, thus destroying it's usefulness to the heater/ AC system, and fabricating a duct from there to a fabricated bonnet around the carb/ EFI body

3....Some other scheme involving chopping up the fenders to install ducts, or routing various kinds of ductwork down to the grille or under the bumper.