questions on timing an engine

67Dart273 said

DO NOT GET HUNG UP on 3000 RPM. You MUST rev the engine to a high (but safe) RPM to be SURE that the mechanical is "all in." If you are concerned about doing this, simply unhook the fan belt long enough to check the timing, so the fan and alternator are stopped.

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EXACTLY!

Bring the rpm up until it stops advancing. Any other reading at a lower rpm is absolutely irrelevent.

If you found where the engine likes initial, any time you dial back the total timing by turning the distributor, you've reduced initial timing. You need to get into the distributor and adjust/reduce the mechanical advance.