ok - I got a set of Melling MPR-667 (6.792" - and they measure out almost dead nuts), and installed two of 'em, along with re-installing fresh snap rings. With zero-lash of 6.764 these Melling 6.792s should be perfect...at least on paper.

Bottom line - it's good...I think. If I'm measuring right preload looks to be in the .015 - .020 range, and, when up on a lobe the snap rings will rotate all the way around in their groove. For sure there is positive preload with everything bolted tight, and the snap rings will rotate around without contacting the pushrods.

Topline says the lighter (<.030) preload is just fine, so I'm gonna run it as-is. And I'm hopeful my engine 'chatter' will be all but gone.