The engine side bolts NEED to come out.The mount has to come out of there.The mount rubbers have molded sleeves that stick into the frame rails.The rubber has to be set in place,and the mount slid into place over it.And as Bill says,look for cracks.Sometimes they're diamonded,I guess that's the way to describe it.They will sag and take a set over time.They are easily straightened with a three pound hammer.If they are cracked you can be pretty sure they need a beating to bring them back.It is not a hard job,the hardest part to me is preventing scratches to the fenders while doing it.