I have a 1969 Mach 1 with the 390 -s code and do I need the upper spring that goes from the z-bar to the fire wall? The spring is not listed for the 390 or the 428 cars. I dont have one and I never had one for the last 45 years I owned the car not saying that maybe it should have one. What do you think or did you see one ever on a big block car. (390-428-boss9 -429) Thanks for your time.