I've got a 66 and originally replaced front and rear suspension with all new stock shocks and springs. Moog springs and middle of the road shocks. I then went the air bag route in the test springs as well. After much wrestling and back and forth in regards to ride height and ride quality, I ended up tearing it all out and replacing it all with QA1 adjustable coilover shocks all the way around. Hind sight being 20/20 I wish I had gone the coilover route from day one. They give you complete adjustability in ride height, I like mine a little higher in the rear, and also ride quality with the valving adjustment knob on the base of each coilover. At the end of it all the coilovers have transformed her into driving like a modern car and replaced the "pillowy" floating ride you get in these old cars, especially on the highway, with essentially a modern suspension. At 70 mph on the highway I now get the slight drop and rebound you do with a modern car when going over bumps, whereas previously the car would float and rock front to back as you get with old school springs and shocks. Granted there are higher dollar springs and shocks out there that solve that problem too, to some degree. But they don't allow for the ride height and ride quality adjustability that the coilovers do. So basically for slightly under $1,000 I've got a much more responsive ride that I can adjust down at the turn of a knob to achieve as soft a ride as I like, or turn up for a more stiff ride, with the additional benefit of being able to raise and lower the front and back end to wherever I like it. Which additionally helps level out the "lean" to one side or the other that these old cars can have too. My two cents, hope it helps.