Before you take the bed off, i would give the tank, and filler a good cleaning and examine the filler closely. old bolts in the bed are a PAIN in the ASS to remove, and will probably need to be replaced as usually 1 or 2 will bust while trying to take them off. I can't see a small pin hole screwing with the filler. Take a good look at what is going on or you might be heading down a rabbit hole that needs not be ventured into.
I have just last night taken off the box of my 92 because the fuel pump caved in, decided the box off would be the worst of the 2 evils. 2 bolts were rusted to hell, one needed the cut off wheel to remove, and the other busted in half and needed some curse words to get out of the nut/holder. Know what you are getting into before you jump into a bigger problem.
cheers