If your removing the gas tank, I slid a board under mine, put a hole in the board, put a threaded rod through the hole, and then put the rod through a fence post that was across the gunnels, and screwed it out. It worked pretty good, and I was able to remove it by myself.
Those tabs on the gass tank are what they used to "push" the tank down into the foam and hold it in place while it cured. I don't think they are "structural" mounting pieces, since they would not hold the weight of 600+ pounds of gas.
I am using neopreme closed cell strips, 2" wide under mine
strips. I am running 3 them bow to stern, so any water can run right out, and have put drain holes in the front and back bulkheads. I am using NO foam on this, as it seems the majority of the the corrosion is where wet foam touches the tank.
BTW, don't be surprised if the deck the gas tank is on is soaked with water, or weak. Most are, and if it's not tied well to the stringers, you might want to address that now. I believe that is structural to the hulls.