What PBR said.
My understanding from the induction system masters: In general, if the throat is round, the throat diameter is 85%-92% of the valve OD. 85% on the conservative side or for low valve seat angles and 92% being toward the race end of the spectrum with steeper seat angles. 93% is nearly always too large. The throat size, shape and concentricity with the valve stem are variable and tunable.
As far as the port and valve being independent - not really. The most important part of the port is the valve & seats (the venturi area), 1" in front of the valve (to set the air up to enter the venturi) and 1" after the valve (to efficiently get the air out of the venturi).
Corrections to this information are welcome.