Need help with parts selections.

[MiracleMax]

BTW, the DD2000 also lists VE! which can help in carb selection. Which on the GT40p engine is in the region of 90% So if your looking at airflow at peak power. the formula would be;

Carb Size=(((CIDxRPM)/3456)xVE)
CID=Cubic Inch Displacement of Engine
RPM=Revolutions Per Minute
VE=Volumetric Efficiency

(((357.2x5500)/3456)x.90)=512 cfm

Thats at peak power, however you might want to base it more on where power takes a nose dive at 6500 rpm where it would be 605 cfm. Especially based on Merc's reccomendation of using a smaller carb with an auto. Also however on a dualplane manifold you can get away with more carb (divided plenum cuts CFM in half) and the signal is stronger to the carb than an open plenum.