For what it is worth;
I have gotten over 600 hp with single 4 barrel 780 vacuum carb on a BB 454 type streetable engine. I have gotten close to 600 hp on a single 4 barrel single plane Tem G and Vic Jr with the 750 Demon Mechanical secondary carbs with 385 cu in and also with 406 cu in engines.
What you already own has potential.
Ed