Unfortunately there isnt' much in the way of small 4bbl carbs. The 390 was what I had in mind when I read the thread title.
390 should be plenty of air to feed a 2.0L The next step up that I can think of is a 600.
What's got you thinking the carb is small? I know you've done a lot of work to the motor, what's been done to the carb? Jet sizes? squirter sizes? what size accelerator pump shot and which pump cam? What do the plugs look like after a WOT shot? How does the motor react off idle? in the midde? and at WOT?
What ignition are you using and how do you have it timed? l