Well there are a lot of options but in the rear you can swap leaf springs , Hotchkiss offers some good handling upgrade packages or Espo can supply new springs similar to stock with different arcs allowing for adjustment to the ride height . when the springs are flatter & lower the car will handle better .
In front It is generally considered that the cars are under sprung by todays standards so larger bars are available from Hotchkiss or PST , .96 diameter would be a minimum upgrade .
Bigger sway bars are a big plus both front & rear the best rear bars are from Firm feel or Hotchkiss but hang on the frame & link down to the diff , in front Hotchkiss offers some very light but much stiffer hollow sway bars .
IMO the most critical part is the Shocks , a premium shock is important , Bilstein is among the best , double adjustable shocks like QA1 are awesome also .
The design of the factory suspension is very good for the day & with good parts can corner at over 1G .