39's are narrower by 3 inch's, also the round hinge/pivit part is different diameter. you'll need a 41 and up tailgate. Check this link out....

http://www.oldchevytrucks.com/blog/index.php/2010/02/1940-tailgate-hinge/

Last edited by JCKN; 12/19/2012 9:35 PM.