any advantages to downdraft carb & header..??

[Sunnybaba]

Hi, just bought a 1930 coupe with completely rebuilt stock engine... I am wondering if I bought a downdraft intake manifold, with weber carb.... and bought a cast iron exhaust header... would that really up the horsepower any..? I know it would make it breath better... but would it have better acceleration.? poorer gas mileage.? what are the advantages and disadvantages.... ?? I want to know from those who have done it or know someone who did.... Before I put out The $1,000..... Thanks