I personally steer away from both Seloc/Clymer manuals. From what I've learned here they tend to cover a range of engines in those books and not specific to any year or HP model. Sort of like the Haynes/Chiltons manuals for the automotive world.
The factory service manuals are the way to go. Those cover all the details of your particular engine.
Check to see of your local library has a subscription to the EBSCO small engine repair reference center. They have service manuals that go back the the mid 50s.