Box Install

[hogfarm]

Well I am almost ready to put the box back on my 54 Chevy.I have a problem. when I took off the bed I could notreach the nuts under the frame,so I cut the heads off and pulled the box,with wood still installed.Now it is time to put box on and I cant see how I am going to get to the hold down nuts.Do I need to put box on with no wood installed? that would be very hard to do,gas tank is in the way and there would be a lot of bolts to tighten from under the truck,can I drill a large hole to get socket in from bottom