That leaky plug at the back is in the water jacket. The cover plug for the cam is lower, and on the passenger's side of the engine behind the pushrod cover.

Any engine that has been running recently is rebuildable, as long as there are no serious cracks anywhere. You'll need to do a complete teardown to bare bones- - - -block, cylinder head, crankshaft, etc. Measure everything, including cylinder taper, crankshaft journal diameter, bore size, etc. Do whatever machining is necessary to rebuild it properly- - - - -don't take any shortcuts.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!