there is a product called BED BOLTS that could be used to secure a box to a wooden bed
the NUT portion of BED BOLTS is a 5/8" diameter bolt w/ a 3/8 threaded hole down the center
their original purpose is for having removable eye bolts in a pick up or trailer bed leaving the bed fully useable when the eye bolt is removed
in a pick up bed the head of the bolt is lower than the ridges in the metal bed
in a wooden floored trailer the head sucks down into the wood leaving a flush surface when the eye bolt is removed
http://www.bedbolts.comsimply drill a 5/8" hole thru the wooden bed and metal trailer frame, insert the BED BOLT, secure w/ the nut, flat & lock washers and you have a good threaded 3/8" recepticle for thru bolting the camper box to the trailer frame
btw, TRACTOR SUPPLY carries a similar product using a 3/8 bolt
http://www.tractorsupply.com/tsc/produc ... -pack-of-2and a heavier 1/2" bolt unit
http://www.tractorsupply.com/tsc/produc ... -pack-of-2they're all sold in pairs from $10 - $16/pair
hope this helps
sw