Look for rust at the mounting points of the K-Frame. Also check the K-frame at the same point. Road Salt tends to catch there and rust.
Look for rust along the trunk floor edges towards the rear of the trunk.
Also look for rust in the tips of the rear quarters above the bumper and beside the trunk lid. They rust from the inside out so if it isn't rusted dig the seam sealer out and treat it before it does.
Also check the usual spots, bottom of the quarters, Bottom of the front fenders, and inside the cowl.