Agreed. The jugs have been off at some point.
Do what mechanics are needed like fixing leaks and threads. A spline lube might be in order and this job is a good way to get at some of the harder to reach systems for checking. If there is oil on the shelf under the trans it may be from the engine rear oil seal. This job and checking the clutch wear can be done when the rear oil seal is done.
Often neglected in these discussions of where to proceed with the resurrection of an older machine is the wheel bearings. The wheels will come off and the bearings removed to check their condition and if replaced then they will be clean and properly adjusted. The same bearings are in the swing arm.
All possible directions of course. The machine will tell you what it needs, of course.
A very nice original condition bike, good patina. It is original only once. Please do not restore, repaint, if possible. Fix and repair. Ride it. Keep the original paint. No repaint is every worth as much as what you have there.