SL-6 Timing is What???

If it is running well, I would leave it alone. Sometimes you just have to find your engine's sweet spot.
That being said, you should verify that the balancer hasn't slipped (not uncommon on older engines). Just verify that the balancer mark is at zero when the #1 piston is at Top Dead Center. If the balancer has slipped, you won't really know where the timing is set.