Initial lead? 408, pump gas,

If your carb is good for idle and off idle transition set your initial timing for best vacuum and idle quality in gear. Heat soak the motor and see if the start is good. Back off slightly if kick back occurs. I run my 340 10.5:1 RHS LAX heads at 28* initial 34 total on 93 pump gas. After you get the mechanical timing setup move on to vacuum advance. I run ported vacuum starting around 6" of vacuum, every motor is different and it's time consuming to get it right.