The valley pan most associated with being from a '57 'E' has a concave flat section to permit the mounting of the aluminum intake on the cylinder heads.
Some say that there were some early production '57 'E' engines that used the late '56 Ford model year, over-the-parts-counter-only, 2x4 power pack application only, flat valley pans. Some argue about this stuff...
If you go to eBay motors and use their search function, search for item 3310770277519. This is a quality reproduction. NOTE: When eBay item 310770277519 opens, toggle the 'sold' picture, then scroll down the page to see the original listing and the pictures that are part of the seller's description.
Another repo Ford 2x4 valley pan that is presently listed on eBay is item number 350857983663
None of the usually identified as '57 'E' style concave flat section valley pans are presently listed on 'E' bay and I don't have a picture to post.
Regards,
NoShortcuts
a.k.a. Charlie Brown
near Syracuse, New York