I think in general the factory engineers spend considerable time and testing to discover the timing for best power and efficiency. The service departments were given some latitude on timing based on customer and fuel quality available. The main differences in timing between mopar electronic and single point distributor will be the at high rpm, the electronic will lose some timing. If the advance is maxed out by 3000 rpm, you might notice 2-4 degrees less timing at 6000 rpm.
Do what seems to run best. Its just that opening the throttle too much at idle should not be needed and the engine should run nice fully warmed up at 650 rpm. You're close. When the initial timing is increased (10* to 12*) the rpms in neutral will go up. I'd suggest when the engine is fully warmed after a drive reset the throttle to 650 or 700 rpm, timing at 12*. Then adjust the idle fuel mixture for best vacuum by turning the screws in (leaner) until the rpm or vacuum drops, then richer until it just returns and then another 1/8 or 1/4 turn more (richer) depending on how sensitive it is.
Plug the vacuum line. Always set initial and test mechanical advance without the vacuum advance. Is this the Mopar Performance distributor made by Mallory?
Crazy late spring for everyone this year - but at least we're done with snow and salt here.
