Are you sure that the timing is all in by 3,000 rpm? If the springs are heavy enough that centrifugal isn't starting until 2k, I wouldn't expect total to arrive until around 4-5k. Keep in mind that changing springs (unless they're REALLY heavy) won't change the amount of centrifugal, only where it starts and ends. Big cams definitely like lots of initial and one way to get it without the usual ill effects is to use manifold vacuum for the vacuum advance with a B28 canister. The B28 fully deploys at only 8" vacuum so you shouldn't get the timing variation (and the resulting idle variation) the other cans would cause. In most cases, the increased idle timing permits a lower idle rpm, which in turn can reduce the chances of run-on that's common with high idle speeds.