Everyone complains what a travesty it was that the smog era robbed the American V8 engines of their performance; carburetor tuning was the major factor in the reduction of horsepower. Ford's '73 and '74 4300D carburetors rob the engine of about 90 horsepower compared to a carburetor in a "pre-1968" state of tune. The fuel bowl is also too small, and is credited for causing a stumble when accelerating out of corners. The booster venturis are quite crude as well compared to the annular booster venturis employed in Ford's earlier 4100 series carburetors.
I find it hard to believe that anyone would want to utilize a 4300 series carburetor. Its like driving the car with 2 plug wires removed. Placing originality above "functionality" is not my bag, especially since a carburetor cannot be seen when the air cleaner assembly is installed. Nobody will notice what carburetor the engine is equipped with … but the driver WILL notice the car's improved acceleration (0 to 60 will drop from 8 seconds to 6 seconds). Thus I am an advocate for replacing 4300D carburetors with better carburetors.
Ray I mention this not to change your mind necessarily, but to simply make sure you (and others) are aware of this situation.
The hole you indicated provides exhaust gas to heat the carburetor and supply exhaust gas to the EGR valve. To disable it thread the hole and screw-in an Allen head type lock screw.
Even with that small hole blocked exhaust heat is still supplied to the cross-over passage below the manifold. You should use the turkey pan type intake manifold gasket, because it provides a heat shield which prevents the motor oil from splashing against the "hot" exhaust heat passage which runs beneath the intake manifold.
If you wish to use the 4300D carburetor, but you don't plan to use EGR, then perhaps consider installing the 1972 intake manifold (D1ZE casting number). It has the spread bore configuration but lacks the big EGR passage on the right hand side.
