Do a search for timing, power timing, etc... lots of threads on it. Many things enter into the equation as to what your engine will need for timing. You'll want more initial timing than 4, and limit the mechanical. Vacuum advance is good for a street car during cruise situations, useless on a race only application, since your at WOT and nearly no vacuum during the run. You'll be more interested in your total timing. Get it in as early as your engine and fuel will allow. Anyway do a search and you'll find lots on the subject.
1970 GSX Stage 1 auto (QQ)
1970 GS455 conv. auto (Red)
1964 Skylark conv.
1970 GS Stage 1 (street/strip) former Car Craft Mag. RSE car. 10.96 @ 124.55 mph, full exhaust, MT ET Street Radials, pump gas.