Imo the stock 273 4bbl intake will really choke the 408. If you go with a duel plane intake a Carter carb will be higher then a Holley. The base where the 273 air cleaner will be to high with a duel plane intake. Needs a drop base. And no one makes a drop base foe a 10 inch air cleaner. Tough to make a good running 408 look like a 273. IMO