Fordboy, I am building a 320" GMC six cylinder. Stock cylinder head with some port work, and a plenum type intake.
There's a couple of pictures, http://www.landracing.com/forum/index.php/topic,12252.330.html towards the bottom of the page.
There are more knowledgeable carburetor guys on the board, than I am. Especially for modified Holley stuff. But having said that, some advice:
A) If you are going to dyno test, weld small 1/8th NPT bungs in the top of your intake runners. Being able to record vacuum during "pulls, (even 1 tap at a time) may prove "insightful". BTW, do not presume 3 separate vacuum gauges will read identically, if you go that route. Pay to have any you use, calibrated.
2) Choose your carb size based on
measured flow of the carb, Vs theoretical engine air capacity * x % Volumetric efficiency,
in the rpm range you intend to use. This will give you a low/high number to select a carb. You will need someone experienced with your engine to suggest a probable V/E %. Or, you will need to flow the whole inlet tract, and then run a computer simulation based on the flow/displacement/geometry.
d) If you don't know how to do the above,
BUY & READ "Performance Automotive Engine Math" by J Baechtel. Also
BUY & READ "Engine Airflow" by Harold Bettes.
HB2 or Dynoroom may be able to recommend a carb size from their experience. But be prepared to do the math on your own anyway. That way you learn something.
Fordboy