Steve,
For Dave and me, what is the "taper adapter"?
Tend to agree w/ JWTaylor. Runout of the chuck body O.D. is irrelevant. Don't the Oneway chucks have straight jaws? if so, chucking a short, clean piece of CRS or the equivalent might be the way to check runout. Can't get very excited about .006 runout. My cheap (oops, economy) chuck is much worse than that, but grips the wood well and rotates it. And after just a little extra spot sanding a couple tear out places, the piece isn't round anymore, even if it was perfect a few minutes ago.
Chakajo- Runout is often measured with a dial indicator. One might use a magnetic base to hold the d.i. The base would be "stuck" to the lathe ways and the indicator positioned on centerline with the tip against the chuck O.D. or whatever one is checking. The spindle is rotated by hand and the total range of movement is indicated by the d.i. Hope this helps.