Slant 6 engine ignition timing stays retarded.

You need to verify the notch on the balancer accurately corresponds to true TDC before you do anything else. The rubber ring can deteriorate over time and cause the outer ring of the balancer to slip on the inner hub. If the timing mark on it no longer accurately aligns with your timing pointer, nothing you do will fix that until you verify TDC with your #1 piston and see if it corresponds with your timing mark and pointer...