I don't hwve a clue where to find the info but I'm cleaning out the bed of my flareside tomorrow and I'll try to remember to get some photos. The bed bolts are a large countersunk head kind of thing. I had to find a nut for one and it was a fine thread, I don't remember the size but the bolt itself was nothing I could find in the local hardware store. The usual retail suspects (LMC< Dennis Carpenter, etc) have bed bolt kits starting around $30.
http://www.lmctruck.com/icatalog/FB/full.aspx?page=26 This page from LMC's catalog might answer a few of your questions.