At the advice of all here with a tip of the hat to AdrzejM I added more block off on the grill itself. I blocked off the right side from behind. I have included a photo here of the right side with the block and the left without. From normal viewing angles you cannot tell the right side is blocked off. I used .062 aluminum sheet stock and painted it black.
Here is the math. Counting the hole in the bumper, by the time I block off the left side of the grill I will have blocked off a total of 340 square inches of opening, and am leaving 112 open to the air. Do you think I have over done the block offs?. I have a large 16" electric fan with a full shroud, which has two speeds and a cross flow aluminum radiator. I am also running Evans coolant. Thanks for giving the information to know what to do here. The block on the right side was easier than I thought it would be. It took a fair amount of trimming and fitting, but did not require removing anything except the upper aluminum air flow panel.
Right side with block off.
Here is the left side without the rear block added yet. Note the wires and such showing.
Sam