I have the bed all in (loose still) sides on, and bed front on. When I install the tailgate "hinges" and hang the gate, there is not enough clearance to open and close the tailgate, it binds on the rear cross member, all parts original, except the cross member, any ideas? Or any one else encounter this?

1950 1/2 ton

Restoring 1950, 5 window, 1/2 ton, in family since new. Never done one before.