Johnson, I would first verify the ignition timing. This could be done in two ways:
1) with the engine off, bring #1 up on compression to the top and check that the balancer lines up with 0 on the tab.
2) loosen the distributor hold down bolt a bit and with the engine idling, try rotating the distributor each way to see if it makes an obvious improvement.
Also, where is the vacuum line from the vacuum advance connected? Above or below the throttle plate (ported vs. manifold)?
Greg
