5 qts plus about 3/4 for a std filter. Your dipstick was modified by Ford to exactly 34.0 inches long from the edge of the top plug to the tip. If it isn't (and I've seen a few that weren't), you should make it so, or calibrate what you have as you add oil to keep from over- or under-filling. The Boss 351C was spec'ed for 6 qts with the very same block, pan & an unmodified dipstick, so a little more won't hurt as much as adding less.
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