I'll add a little more info to Beast's comments. IIRC, the recommendation for 6 qt is from the owner's manual for a 2 valve Mustang. The Cobra supplement recommends 6.5 qt. But the heads can hold a lot of oil when running high rpm. Running 7 qt helps prevent the oil pick up from sucking air. The additional oil doesn't contribute to windage though -- an SVTP member took some pictures of a stock oil pan w/increasing amounts of water in it. At 7 qt the oil level will still be far from the crank. The clearance will increase when the engine is running since some of the oil will be circulating in the engine.
