8' long beds came in both metal and wood, so do Longhorn...(and SWB for that matter).
The wood bed rear most cross member is different to the metal ones, with a height difference of approx 3/4" to 7/8".
The height difference is to permit the difference in thickness of the wood bed and the metal beds.
If you check out this link, Item 5 in each of the bottom frames...they are different...
http://www.lmctruck.com/icatalog/cb/full.aspx?Page=14
