See the G Force Crossmember Overview
for more info.
For vehicles originally equipped with 3/8″ crossmember bolts, open existing holes on the frame to 1/2″. If you prefer to retain 3/8″fasteners, upgrade the installatin hardware to Grade 8 bolts and hardened flat washers.
Some minor contact between the floorplan and the crossmember may occur due to body bushing settling and deterioration, or a bowed floor pan. Usually, this is not a problem. A hydraulic floor jack with a wood cushion will correct a bowed floor.