Before you do any cutting, remove the gas tank. Early A-Bodies used a single strap from framerail to framerail to hold it in place. Simply unhook the hose to the fuel pump and the fuel-gauge wire, and then loosen the stud holding the strap. Oh yeah, it's easier if you empty the gas tank before removal. Before you start cutting out the floorpan, make sure all wires (like those to the taillights) are moved so they don't get damaged.