Well... turns out the parts diagram I was working from is an older version that does not show the ET173/1 shim that goes on the idler shaft. If I a shim behind the idler, I can move the idler out .015 So that leaves the cam pinions off by .015 relative to the idler. Assuming I don’t need a thrust washer between the idler and the ET173. They list the ET173 as a thrust washer so should be hard enough for the job.
Rip (as well as others) mention needing a minimum of .015” end float on the timed breather (everything else .004 to .008”). This has a series D breather, so what is normally a timed breather is actually just a small idler running on a bronze bushing the same size as what the earlier breather would be. Given bronze expands at a lower rate, I’m assuming .012“ end float is sufficient.