[John Brown]

That looks like a number 6425 Holley 650 cfm two barrel with the choke horn cut off, or it could also be a severely modified 4412 500 cfm carb. I used to run two 6425's on an STR-10 Edelbrock in an IHRA multi carb class. Holley sold three or four inch chromed stacks that fit onto the air horn for even better flow. 6425 is an annular flow carb. Nothing to interupt air flow, since the fuel comes in through the sides of the 'barrels'.