2cents...clevis' as part of my trade /profession of 43 yrs I have never heard it pronounced as "cleevis"..and to settle the east /west thing I'm from the 3rd (Gulf) coast and we say it with a short E as well..call it a Cleavage Pin just to stir the sh%t..out.
Worked on airplanes and boats around the world for 50+ years and never heard "cleevis." Saying such a thing would probably get a person laughed at, as even the Brits pronounce it with a short e.