You Can use a sawsall but I don`t recommend it , the piece you see in the picture is the trans crossmember & cannot be cut into as it aslo supports the torsion bars , the shift rods go between the crossmember & the floor panel/ hump you are installing , do the same as in the picture mark around the hump with a marker & cut 1-2" inside that line & trim as nessisary , I use an angle grinder with a thin cut disc to cut the floor , grind the sheet metal away from the spot welds as well & if it starts to cut hard Stop, as you are probably cutting more than just the sheet metal