I have a 1967 pontiac lemans that originally had an inline 6 ohc, but now has a 389 bored over 60. The car has gabriel hijacker air shocks that are bad and am looking to buy the same thing. The two that fit my car have a light duty and heavy duty suspension, but I'm not sure which one I need. So if anyone has information on if my car has heavy duty or normal suspension. Thanks in advance!