need tuning help on 340

Don't worry about vac advance right now.
Get a tach and check the timing at idle rpm, then 1000, 1200, etc. to 2800 or 3000, and 4000 if you want.
Damage from detonation will happen when there is high load on the engine. Not when idling in neutral or cruising.
It (detonation) will first show as tiny metal specs on the spark plug porcelain. A little worse and you will hear it 'ping'.
Keep your ears open, and if your concerned, stay out of wide open throttle, especially in 3rd or 4th gear.