I believe you answered your own question,
You stated the pass spring has been replaced, you should buy another one, check with last owner what part number he bought, or just buy a new pair and replace the set. And new rubbers to go with them.
Make sure the front subframe is parallel to the floor(of the car) underneath. As with age in all of us, we may sag in a few places, one place would be the rear mounting bolt under the seats. The frame may start to pull the floor down, and using the firewall as a fulcum, the front wheel goes up, therefore, giving the car a lean to one side.
Quarterpanels can be installed alittle off at time of replacement, but, they don't support thr wheel(s). They do help in triangulation of supporting the components with the weight-bearing loads.
Anyway, enjoy the ride, I used to have a 68 327/4-spd plain jane, wished I never would have sold it, but, life goes on, then we die.
Keep us informed as to what you find....