only way I'd ever do it, cover the tank and lines with a welding blanket or something, drill a hole in the bed and use shears. sawzall would be next but it sparks too.
Most ppl do one of the 3 that's why I said it. it's either remove bed, drop tank or cut access hole.
I would never cut a hole over the tank for any reason good shape or not, too much of a risk, for me dropping the tank is much easier then a bed anyday.
There is only one bolt that's the rear strap to remove, in the back and strap doesn't need cut or anything, the front has a 4 bolt crossmember with strap that can be unbolted and dropped down and out, same way I did mine. My bolts were stripped and way too tight so I ground their heads off, knocked them out of the bracket once the tank was out(they press in like wheel studs) and replaced with bolts, washers, lockwashers, lock nuts and loctite.
The rear bolt is in the bed crosssill under the truck closest to the driveshaft and it's 18 or 15mm head, the side frame bolts are near the back cab mount and 4 of them(pretty sure, might be 3) and they are either 13 or 15mm heads, I done mine last summer so I'm a bit foggy.
On a side note once my rear was loose, I loosened the front strap not the crossmember/bracket and the back of the tank would drop a good bit, so might want to try and loosen those strap bolts and see if it drops enough to get in and work.