Otis, the needle on a factory amp meter will ALWAYS dance around because the factory wiring routs 100% of the alt output thru the gauge, and starting the engine always uses some battery power.
Many of us install a large gauge 'shunt' across the amp gauge posts to relieve some load from the gauge. The proportion of shunt surface area relative to the gauge innards reduces needle deflection, so use the biggest wire you have available (or a piece of brass shim stock) and double-insulate it with shrink wrap.
Sure- it makes the needle 'inaccurate' but no one can accurately read a flickering needle anyway. The amp gauge is really an idiot light showing 'some' alt charge- or not.