The Carter is set up for the "AFB" flange configuration, with 2 additional holes in the "Holley" configuration. The flange is plenty large to mill 2 additional holes so it will fit the "Holley" configuration. Have seen many of them that have been modified with the extra 2 holes (total of 8).
The issue with the 9400 is that Carter made the last one about 1980; they are very much in demand, and fairly pricey.
Jon.
