68-72 Nova owners come on in..

[BLACKLS5]

First I want to say that I have always owned Chevelles so I'm still learning the Nova stuff. I bought a 70 Nova SS a little over a year ago and as much as I like the looks and driving something other than the Chevelle on occasion this thing rides like a log wagon. I just got it out of storage today and man this thing rides rough. Since I bought it I have replaced the air shocks and 3" aluminum spacers with standard shocks and have also swapped out the "hang'em high" shackles with stock type stuff. I see no difference in ride quality. This does have the original 12-bolt axle with multi leaf springs. Do they all ride this hard in the rear? This car has no traction aids and no sub frame connectors. Pretty much stock. Any suggestions or is this the nature of the beast? Honestly I can't believe the General could sell anything that rides this hard to the general public back in the day so I must be missing something. HELP...