[frnkeore]

Here is some original Ford dimensions that you can do the math from.

The center to center distance of center of the bore, to the center of the lower stud is 1.937.

The distance from the center of the bore, to the outside of the casting is 2.31.

Now, if they did use 24 stud cores, you could bore it 3.312 but, if they used 21 stud cores, the outside core diameter is 3.38.