Signs of wear?

I'm at the advanced stages of stripping down my 1969 st 70 and I'm wondering what parts I really need to replace.There are some parts on the folks that I can see are worn out and obviously need to be replaced.But the white plastic bushings in the folks,for example, have cleaned up really well and to my inexperienced eyes seem to be in good condition. Should I change a part just because its 30 years old? Same for the rear spocket and the black rubber(?) dampners,they look ok to me when cleaned up.What should I be looking for in terms of wear and what are peoples opinions of definite replacement items,regardless of appearances?

I would strongly suggest to replace all of the parts you mentioned.
It's better to have them replaced now you go trough all the effort, than having to replace them within the next year.
Dirt isn't a problem, but rubber gets harder with the years and gets deformed.