AED 500 cfm carb
The cheap speedway, or summit carbs are not worth buying, we see on the average of 20+ horsepower when switching to one of our AED 500 series carburetors. One of the best investments you can buy for your racecar to gain overall horsepower is buy a good carburetor.
They cheap carbs work ok if you get one that has no core shift in the main body. The Holley 2 barrel carb is the touchiest carburetor there is.
As for fitting on the gm intake, you need to buy a Rochester to 4412 carb adapters, which can be purchased most anywhere.