I used to run a 383 with a tunnel ram and 2 600 vac sec holleys. The cam had .500 lift but 300 deg. of duration and I also had 3:23's in it. I think the only thing that made it driveable was the standard transmission. While you can't beat the looks of a 2-4 setup, they pretty much suck on the street. If you must do this then my suggestion would be a set of 450 cfm holleys with vac secondaries. If you go any bigger then I'd suggest you just don't hook up one of the carbs !!