I have a nice Weber 32/36 DGEV carb fitted to my 258 AMC six, using a "Jeep Weber" adapter I got from eBay. The Weber came with a cheap "K&N style" air filter. It's all worn out, and I didn't like it anyways; it's incredibly loud (sucking a few hundred CFM of air is no trivial task) and it sucks hot air indiscriminately under the hood. It also just looks wrong on this car.
So I decided to adapt a vanilla AMC hatbox style air filter assembly to it. It's not much of a project really. I chose a later-model filter (it's from my junkpile, no idea what the donor was) with a rectangular snorkel. I plan to cut a rectangular hole next to the radiator to duct in cool outside air, and to plumb hot air from the exhaust manifold to the temp and vacuum controlled flapper for faster warmups.
First thing I did was cut a round disk of thin steel (stainless steel actually; it's what I had laying around) using the new filter element as a pattern; I cut the bottom of the donor filter box out smaller than this disk, then held it over the engine in the car to make sure it would fit, and work out alignment, and marked it with a Sharpie.
Using the old Weber filter base I traced the complicated rectangular-ish hole onto the stainless disk; for each of the rounded corners I center punched it in about 1/4", then drilled holes at the punch marks (1/8" followed by 1/2") and used a sabre saw (jig saw, whatever you call it) to cut out between the holes, and spent a half hour or so filing it to match the old Weber filter base.
Now this stainless steel disk fits onto the actual carb; so back out to the car I went. Now I could hold all the components in place, by hand, to make double-sure it fits. It cleared all the hoses, valve cover, fuel line, etc, though it was close to the top of the carb in front. Back to the bench.
The stock setup has a stud that screws into the center of the carb, and the filter assembly is held to the carb with a wingnut. The Weber has no center stud; instead, the Weber airfilter bolts to the top of the carb with four small bolts. I bent a piece of 2" wide steel (1/8" thick) (again, what I had laying about in the lab) to fit within the air air filter, and just barely clear the cover.
It took four tries; two became scrap, I was able to un-bend the last bad bend using a propane torch and hammer.
You can see here the exotic tools I used for this job. The final bracket came out pretty good. You can see all the duds and scrap in the background.
Because it goes over the top of the carburetor when assembled, and could interfere with airflow, I cut out excess metal with the sabre saw, following some freehand Sharpie markings. The final shape came out so nice, and reminded me of 19th century blacksmith work, file marks and all, that I left this part unpainted.
Not visible are the four holes, two in each end, in the bracket that goes over the carb; these are tapped and #10 machine screws bolt it to the stainless disk from underneath. I then placed the top cover on, then marked and drilled the center hole for a gen-you-wine AMC air filter wing-bolt.
The whole thing got a thick coat of black wrinkle paint (the Eastwood Company sells it) which is very rugged, matches the valve cover, and not accidentally, hides a lot of small imperfections.
Voila! Quiet, clean and cool air!