I've had (have
) a lot of these bikes so here is my take on what you've acquired.
I believe your bike began life as a 1975 CB550K model. Frame, tank, and foot pegs are correct or that model.
The exhaust is from an F model, and I expect you will have problems with the brake arm and kick start lever interference. I've yet to see any successful graft of the F exhaust system onto a K model. You have less headaches with that interference and fitment using almost any other muffler system.
Looks like the seat is also from an F model which is why it fits so badly on the bike.
Someone, has tossed the air filter box and put on a K&N single filter in its place. It needs a cleaning and re-oiling, at least. But, it gives no protection from rain or road grunge, so best to learn how to clean it as it will need that frequently.
The lack of center stand (it's been removed) means you are going to need a lift of some kind during resurrection.
Since you oiled the front brake pads, you will now have to replace them. FYI , the next time you encounter a frozen front caliper just loosen the two caliper bolts, and you can probably reuse uncontaminated pads.
Shouldn't take too much to make that bike streetable. Brake rebuilds, tires battery, fluids, fork seals and cleaning. Get a K model seat from a 72-73 CB500 or 74-76 Cb550 K. And get an exhaust for those years, you should be good to go.
Lastly, clean and polish the fuse clips to prevent a fuse box melt down. And to prevent nagging electrical issues/stoppages, clean all the connectors in the wiring. Don't ever, I mean ever, connect a battery with reverse polarity. Smoke flame and damage WILL occur.
Also, don't take off the cam cover without paying special attention to the shop manual, or risk bending valves.
Use 0000 steel wool on the chrome bits. You'll be surprised how much better it will look.
I caution the use of a straight wall plug socket on the spark plugs, particularly during installation. The tool kit socket was bell shaped to clear the obstructions in the access tunnel. A straight wall tends to angle the plug during install, cross threading the spark plugs, and steel is tougher than the aluminum head.
Cheers,
Edit: punctuation and improper pronouns.