Occasionally there is a 6375 RPM reading in the log and that is almost always due to the air gap with the reluctor being a bit too wide or an irregularity in distributor shaft that the reluctor rides on or sometimes even a tooth of the reluctor being a few thousandths of an inch too tall. It’s pretty easy to resolve. The distributor must be  removed to check the gap as you turn it by hand. If there is a tooth too tall a few strokes with a points file  will take care of it. I also hold it up to a light to check that the reluctor tooth is parallel to the pole piece  of the pick up coil and if it’s not a little pressure on the pick-up takes care of that. Set the gap as close as  possible but make sure no teeth touch the pole piece. As you spin it by hand you can hear if a tooth touches and  feel the magnetic attraction of the components. I use a small strip of copy paper folded into three layers  between the tooth and the pole piece and then use the adjustment screw to just pinch the paper. Rotate the distributor  to loosen the grip on the paper and see how it looks/feels.