You'll be surprised at how well the 16v battery will spin that motor. If your using the Hitachi starter make sure your using the diesel model. They are more heavy duty than the standard one. I had that setup on my 632 BBC at 15.3 cr and it spins it about like the plugs are out on a 12v setup. I also used a start retard on the ignition which helps a bunch at higher cr.
Also with the 16v it will work with all your 12v stuff.
Blessings........Ron C