Robert,
from yur pics it sure looks like the rear end of your bed is flared out bought 2" to wide buy the tailgate hinges and your bedsides are leanin out.
Just took a quick measure on mine ..me bedsides at the rear are exactly 50" wide inside and my tailgate fits great.
Hope this helps.
Tim


1952 Chevy Shortbed

Photos in Photobucket

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