More timing at idle really helps. I found that out when I installed the EFI system. You might be able to adjust the vacuum advance to pull in at a lower vacuum level and then connect the vacuum advance to full time vacuum source.
Another option could use an ignition retard module triggered with a microswitch on the carb, like a nitrous setup. At idle you could run alot of ignition advance, then when you hit the throttle, the ignition would retard and advance with the distrubitors advance curve.