Never owned an e-body, but have ridden in one nd it did have a nose heavy feel to it. Short trunk + less overhang over the rear,makes the all the pony cars ride rougher as well.
I had a 68 Coronet 500 years ago and it rode very smooth so you can get the old stuff to ride nice enough to go on rod trips with.
Maybe your car needs a firmer steering box and some better shocks, ect?
