Looking to modify 2 barrel air cleaner base to 4 barrel…little help?

Honestly, why not just use a Magnum air cleaner? The Magnum throttle body is 4 bbl. sized, so it bolts right on your carb. It's set up for fresh air ducting. And it came on 3.9s, 5.2s and 5.9s in many different Dakotas, fullsize trucks and vans. And best of all, it sells for peanuts at the boneyards. And looks stock.
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Not all have the Magnum sticker on them- so pick your flavor.