Not many. Most of the divsions in France in 1942 and 1943 were unfit for service in the east. Some had been sent west to reequip & train replacements. Others were static or fortress divsions that had little equipment for field service. They were organized to garrison the fortified ports. A few others were made up of unreliable non Germans. In the winter of 1943 - 44 the rehabilitation of the depleted divsions was accelerated and more men and equipment were diverted from the other fronts for garrisoning France, Belgium, & Holland in anticipation of the Allied attack in 1944.

Had it been possible to reduce the garrison in the west the largest difference would have been in men available for infantry replacements in the east. After that the transport & fuel.