Not knowing what type and how many miles you've driven, I'll take a shot
The normal 'ride & handling related' wear items are the struts & shocks, the rear bellcrank bushing, the tires (duh
and the suspension bushings. If you're ready to replace things due to age, go ahead and see if they bring your PT back up to snuff.
The title of this thread leads me to believe that you're interested in regaining your original ride dynamics, so the OEM parts would be your safest bet.
Brian