Who was originally supposed to play the Tin Man in The Wizard of Oz?

The part of the Tin Woodman originally was assigned to Raymond Wallace Bulcao ka Ray Bolger [January 10, 1904-January 15, 1987]. But Bolger was interested in a role that would showcase his acting, dancing and singing skills. So he persuaded those in charge of making the beloved 1939 film version of 'The Wizard of Oz' to let him switch roles with Christian Rudolph Ebsen, Jr. ka Buddy Ebsen [April 2, 1908-July 6, 2003]. Ebsen originally had been assigned the role of the Scarecrow. Ebsen moved into the role of the Tin Woodman, only to develop a serious allergic reaction to the makeup. Ebsen then was replaced by John Joseph Haley, Jr. ka Jack Haley [August 10, 1898-June 6, 1979].