large 40 gal Aero tank question

[grillzy]

I need to drop my tank. It is the bolt through the floor and tank style with long carriage bolt from the top and I am assuming the flat washer on the underside is the nut (center fits 3/8 drive). I know the nut will not come loose today but may with a few days of wd-40. If not anyone have luck with grinding the head off the bolts and driving them from the top and have the nut come off the tank that way? Then I would just use threaded rod to re install.