Whoa!
Initial (base idle) timing is 30°? That's dangerous, as it will add unknown timing as it revs.
ATK recommends 30 to 34 initial timing.Whoa!
As you do not know the centrifugal advance in your distributor, you can set timing by total (all-in) advance at high-rpm. Disconnect and plug the carb-side of your vacuum advance (if you have it). While watching the timing with the timing light, rev the engine until the timing advance stops adding timing. Note the degrees. Adjust the distributor position until the total timing (all-in) when revving to all-in is 34°.
If it were me, I would confirm exact timing mark location with a $10 spark plug thread timing stop (or make your own). Then if you do not have a dial-back timing light; add measured marks every 5° to 40°, before setting timing as-above. 34° is only a place to begin timing tuning, but should be much closer than guessing, and certainly safer than what it is.
