Good Initial Timing and Too much Total Timing Problem. Seeking guidance to minimize total timing. 1969 Swinger 340 4 Gear

This engine is non-std & has a non-factory carb & headers, both visible in the pic. Does it have other mods? So factory settings can only be useful as a guide once engines are modified.
Even absolutely stock engines can benefit from 'tweaking'. That is because the car maker, not knowing the end use of the car, has to be conservative with the ign timing curve/settings to cover the worst case scenario.