The CFM calculation (CFM = D × RPM × VE ÷ 3,456) is not divided by the number of carburetors for IR. 375 CFM total is not 125 CFM for each of three.
For reasons too lengthy to explain, three individual carburetors for an L6 can, and should, be much larger than three carburetors on a common manifold.
Except for the fabrication, the Weber DGV 32/36 is an excellent choice for IR. Other choices include Rochester 2G, SU HD6, Stromberg 175CD.
