[tdangle]

your idle vacuum as long as it is steady and depending on the cam installed somewhere between 15 and 20 inches is good. Don't worry about it. You will not see your lowest vacuum reading flooring it with no load. The higher the volumetric efficiency of the engine the closer you will come to 0 inches of vacuum. Most street engines are in the area of 70 to 75% VE. In a street engine I doubt you will see lower than 3 inches.

Vacuum advance for your dist will only come into play when the engine is running. at engine cranking rpms I doubt you will get any advance so that wont cause hard starting The vacuum advance comes in for cruising at light to moderate throttle allowing the engine to run more efficiently and get better gas mileage (I'm not sure what the optimal amount of vac advance is)

A good mechanical advance for a SB chevy street engine is somewhere about 32 to 36 degrees all in by 3000 rpm. So 12 initial and 20-24 mechanical advance should give you good performance. Any more advance or a quicker advance could lead to detonation which will kill power (and could hurt your engine)

Good Luck with your project.