If you are serious about restoring your 68, this is not a job for a novice but a professional. It will require some expert body work (cutting and mig welding) to turn out right. The bed (2 pieces I believe) is available from National Parts Depot NPD.
The front smugglers box is bolted in, the other panel is welded (I am pretty sure). The only replacements I have seen are two full panels that split the bed front to back. You can get replacement smuggler box covers if it is just rusted in the front. Now if money is no object, Bruce Horkey Wood and Parts sells a very nice fitted wood show deck (for a cool $960). It still needs a bed to sit on.