The length of the tube isn't really a big deal, but diameter should as large as you can make it (within reason). Atmospheric pressure is pushing air into the lower pressure of the evacuated cylinders. The larger diameter tube will allow larger amounts of air in more easily @ WOT and high RPM, but who drives or wheels with the throttle pinned for more than 1% of the time.
The more you can increase the pressure differential between the cylinders and atmosphere, eg. Turbos or blowers, the oxygen volume goes up allowing for more fuel=more HP.
and more broken parts...we used to run a small 2 barrel on the '68 Blazer/PU cause it made for great low RPM throttle response and was a great rev limiter. Kinda would start to flatten out power wise at about 4000 RPM. Also the little carb didn't puke fuel everywhere on angles...