I did some tests and discovered that the plates (segments in each display) will need to be driven by the full 12 volts while the grids can be supplied by the Arduino's typical 5 volt digital output. This requires me to use a transistor to drive each plate along with a resistor driving the base of each transistor. The circuit (minus the resistors driving the transistors) should look something like this.
It appears I will be using 11 (7 plates + 4 grids) to drive the VFD. This just squeezes into the IO ports available on my Arduino.
Next step will be to get the VFD attached to my protoshield, along with the transistors and resistors so that I can begin writing code... :) Can't wait...