My

. I don't think it is such an issue. Re-build the distributer or use a serviced one with a working capsule and working centrifugal weights. Make sure that if the capsule has a small hole in it at the bottom, then replace it with a small holed one. Get rid of the play on all the moving parts. Set the points at 0.018" and turn the little ratchet cam on the vacuum capsule to mid-range.
Set your timing static at 8-10 degrees. ie turn the engine until the TDC mark is 8-10 degrees BTDC. It will be about 8-10 mm before. Loosen the distributor slightly and turn it clockwise about 10 degrees. Now turn it CCW slowly, with the ignition on, until you see a small spark. Stop there and tighten the clamp.
With the vacuum tube disconnected and plugged, start the car and check with the timing light, it should be right. Rev the car to above 3000 rpm and note the advance. It should advance to about 30 degrees. If so then the centrifugal advance is working.
Connect the vacuum tube and check the advance again with the timing light. It should be advancing more than the previous 30 degrees when held at a steady 3-3500 rpm. This is because there is no load on the engine. If you activate the accelerator fast, the timing should retard back to 30 degrees and when you leave the accelerator it should exceed the previous advance. This is not really necessary but interesting to see.
Now drive the car, it should be spot on for you. If it hunts a little when cruising the ratchet cam can be slacked or tensioned until it is smooth because that means the timing is a little too fast or too slow for the speed.
The figures in the book could be dyno figures of many years ago. In the meantime the engine has a little wear after 50K miles, you are living at a different altitude, you are using a different octane fuel and a better quality fuel, your plug gap may be different. All this affects the specs given by the factory. So why try to get it within a degree or so if all those variants have varied?
Regards, Frans.