You're almost there . I'd mix & match springs so the mech advance starts a couple of hundred RPM above your idle speed in drive which is what the eng will see stoplight to stoplight & then with just enough tension so you are just under the pinging point at WOT up thru the gears on your hottest/driest (most likely to ping) day.
live every 24 hour block of time like it's your last day on earth
. I'd mix & match springs so the mech advance starts a couple of hundred RPM above your idle speed in drive which is what the eng will see stoplight to stoplight & then with just enough tension so you are just under the pinging point at WOT up thru the gears on your hottest/driest (most likely to ping) day.