I have a 69 SS, #'s car, 350 / 350, std interior, non factory A/C. I have the build sheet. There are some things that are missing, and some things that are damaged that need to be repaired / replaced. I would like to know if any of the folliwing parts would make any difference as to it's authenticity:

Oil Pan - mine is damaged. Question: Can I use an oil pan from a 68 smalll block "plain jane"?
Headlight Bezel - Do 68 and 69 interchange?Thanks

Not absolutely sure about the pan (I don't see why not) but..
the 69 headlamp bezels definitely do not interchange with 68.
Maybe you're thinking of 67 or 68 RS headlamp bezels. They are the only 2 that interchange. All else are different, -especially 69.

I believe that all sb oil pans are the same, with the exception of the Z/28 oil pan due the windage tray used.