The BCF's, at least at my company, have had their horizontal stabilizer fuel tanks removed. The purpose built -400 freighters do not have horizontal stabilizer tanks. The -8 Freighter does not have horizontal stabilizer tanks either. The -8 Intercontinental appears to still have the stab tanks; like the -400, its listed fuel quantity is roughly 10,000 kilograms greater than the freighter's.
Granted I'm still an ultra neophyte to the world of 747's and freight, but, it's my understanding that zero fuel weight is the limiting number for the freighters on most missions. Filled to maximum zero fuel weight, the 747-400F can only take on roughly 100,000 kilograms of fuel, over 60,000 kilos shy of capacity even without horizontal stabilizer tanks. The number of missions in which the stabilizer fuel might be used apparently did not justify the cost of the equipment, not to mention the added maintenance. In addition the freighter is already considered "tail heavy" in regard to center of gravity....whether or not that factored into the design process I cannot say.