Gas cap looks a bit odd/like it was replaced with something other than the stock one.
If I was trying to sell it, I'd probably do some clean up work in the engine...a little degreaser would probably make those valve covers look a lot better. Does it have the original air cleaner or an after market one? And what shape is it in?
I think 4K is low, assuming you can find the fender tag/build sheet and it is number's matching. I would think 6-8K with tag, sheet, and verified numbers match. If I was in the market and it was local to me, I might go as high as $10k after inspecting it, and depending on the options the documentation reveals. Other documentation would help drive up the price as well (window sticker, warranty cards, owners manual, etc), at least with the originality crowd.