I have a 67 std with a 302, pretty bare bones. I put 620 coil springs on the front, and notice that around corners around 60-70 mph, it seems the stress from the front end is transferred through the unibody to the rear (They feel horribly mushy)...The rear leafs are shot anyway (1 inch lean to the driver's side), and want to order new ones. I want to go with a stiffer rear, so I am looking at ordering the GT/ Performance Package rear leafs, assuming the heavier springs will stiffen it up. Does this logic make sense? And will the GT/ Performance Package springs raise my rear height?