I am the new owner of a '76 750. I know that I've got a lot to learn about this bike and am nervously looking forward to this experience.
My bike runs OK, but needs a new seat, the rear tail light doesn't work (but the brake light does) and needs the neutral light sorted out. Oh, and while it's pretty clean from the sides and top, the bottom is a mess. Looks like it's been sitting in a tub of sludge. The chain is sagging a bit, but she needs a thorough cleaning before I go much further.
Anyway- I'm happy to have found such a great resource and hope to not come up with anything that hasn't been covered already.