Just finished reworking one 4gc from 2 carbs and some more jets I posted what I did on the what did you do to your gbody today 2024 .carbs were used on gm cars and trucks 1955 to 65.came in 3 sizes the middle size being just about 600 cfm depending on what you can read.If your reworking one I recomend useing the leather type accel/ primer pump