Worth the effort?

It looks like it would be a good project, and for the money its probably not too bad. If the oil looks good (no water, fire extinguisher foam) and it turns over smoothly then itll probably be just fine. Fire extinguisher foam does pit aluminum pretty bad, but a cast iron block and heads are going to be pretty indestructible. You would eventually need a run stand, or a car to put it in to see if you rebuilt it right, and truly enjoy the fruits of your labor! Driving a car with an engine you BUILT is definitely a special feeling.