Try "Mustangs Plus", Stockton, CA. at
www.mustangsplus.com, and 1-800-999-4289. In their catalog on page 184 is the oval "Cobra" air cleaner and on page 185 is the filter element, part #1999 at $19.95. Ford Racing no longer makes them.
www.CJ Pony Parts.com has the filter for $21.95 , also, "National Parts Depot" at 1-800-235-3445 shows one on page 119 for $21.95. On another note, I hope that you can join us this Saturday morning for the run down to Arivaca. John