I'm in the process of restoring my 64 Chevy Fleetside. When I removed the bed and cross sills (they where very rusted) I had to cut the support bars that connect to the panels from the cross sills.
Trying to find a replacement has been very difficult. I found one vendor that carried them, but they where $80 (and on back order with no expected delivery date). So I had to find an alternative.
I went to my local hardware store and picked up four metal braces that carpenters use when building floors.....they go between the floor joists.
They where $0.50 each. They are flexible, yet ridged. They worked great for me and wanted to share with everyone this tip. I attached a link to some pictures to show what I mean.
I hope people find this useful. John
http://photobucket.com/albums/m597/johnnywaz212/64Chevy