There should definitely be a notch in the edge of the harmonic balancer for timing. It may have been painted over or dirty. I usually put a dab of white paint on it once found so it's easier to see under the timing light.

Or, if it's running well enough for a drive, find a steep hill and mash the throttle going up. If you hear pinging let off the gas and pull over to retard the timing a bit. Do the same test until the pinging almost goes away. It may barely ping when you really hit the gas but won't ping during normal driving.

That is usually the best way to find the timing your particular engine and the gas you are using runs best at. The manual has the timing way too retarded in my opinion but they did it for gas economy and having it a little more advanced gets more power and performance.

I've always been told that having the timing too advance can cause overheating problems too so make sure that is dialed in.