To Vacuum Advance or Not to Vacuum Advance
The distributor is a MSD 8388
A possible challenge with using vacuum advance on the MSD distributor may be slowing down the mechanical advance enough.
Lets say the mechanical advance adds 15* by 2500 rpm, and the intial is 20*. So timing at 2500 rpm is 35* BTC
And lets say the car cruising at 45 mph is at 2500 rpm, and the engine is pulling 16"Hg.
If there's a vacuum advance is fully in at 12 "Hg, and it adds 15*, then timing will be 50* while cruising at 45 mph or above.
Squeezing the throttle for an uphill or mild acceleration at 45 or 50 mph very likely will ping.
Only short trips might not happen. On longer runs where the engine gets fully heat soaked, its more likely.
If it does, need to slow the advance.
Most Chrysler distributor curves have two stages. The high performance engines picked up combustion efficiency very quickly off idle, and so got long slow advance curves above 16 or 1800 rpm.
Not all advance mechanisms lend themselves to two stage, and nor is it always needed. With your setup, if you run enough initial, two stage may not be needed.
