harsh ride ..in the rear ?

My 67 nova seems to take bumps and dips in the rode very hard in the rear.I just installed new KYB shocks and it didnt change. So..my question is, Can the rear leafs need re-arching to eliminate this? Or maybe replacement..The cat is a stocker..

Adding new shocks would only make it ride firmer, same with changing the springs--unless you're trying to say it's bottoming out the suspension. Is it sagging in the rear?
Stock mono leaf springs and shocks usually ride pretty soft.

Has multi leaf rear springs..and level stance.

Has multi leaf rear springs..and level stance.

theres your problem its not suppose to have multi leaf it suppose to have mono leaf. meaning single leaf on each side.

just chevy,You say "supposed to have" ? What is the difference,are the multi springs stiffer?

Originally 62-67 Novas came with monoleaf springs. Aftermarket multileaf springs are available, usually having a higher spring rate, which will increase your ride stiffness.

You are "supposed to have" the correct springs for your application. There is no general right or wrong here.