I ended cutting the nut holding bracket off with a cold chisel and welding the nut to the floor on my dads truck, on mine i got out the gas axe and cut the floor out.

If you remove that nut bracket you may beable to smack an old socket on it to hold it
done the same thing got jigsaw cut the floor and chiseld it out,that reminds me i still got to weld the flap i cut
vince