Funny, that'* one of the threads I read last night that got me on the load height bit. If ELC is there for spring rate and the 653 has much more spring rate (nearly double) than the 5711 while both have the same load height, how could the 653 NOT keep the rear level? I'm again assuming an unloaded vehicle. All bets are off once the rear is loaded as the ELC should level the rear. We have specs for the replacement springs in the aftermarket. I've seen the spring codes for various RPO in a thread I read las night, but no specs were listed. Maybe someone should go offer gifts to a GM parts counter employee.