Question How are hickey fuel tanks mounted?

[J_T]

Hello all, I was changing my body mounts But I found that the hickey fuel tank mounts under the frame into the tub. So therefore I can't raise the rear of the tub to swap the body mounts. I believe this tank has through bolts. Is anyone familiar with The type of hardware that is on the underside of the through bolts? It appears to be a flush mount nut but uses a square head? Either way, mine are rusted on and I thought about just grinding off the heads in the tub and dropping everything down But I wanted to confirm that would actually be enough to drop the tank?

Thank you all!!