Ideas on what's causing my click/tick/rattle noise?

can't help with the bearings
but what manufatcuere of rings did you use?
sealed power provide an instruction sheet that is universal to every ring they have ever produced in the last 40 years. as far as i can tell. Lots of pictures, mentions of profiles to inner and outer edges, dykes rings etc some refernce to dots that some rings have and some rings don't . If you buy a set of bog standard or even special material or coated rings for say.... in my case magnum 318 pistons (repurposed for my 265CUI 6). Then the ring installation is covered by the last few sentences on the back of the page which says something along the lines of if it has "inner profile thus and outer profile thus then this way is UP but if not its down but if the rings have dots the dot goes up, but not all rings have dots so use profile to detrmine orientaion. clear as mud. None of the pictures or anything in the extenive text you read in the previos 2 sides of folded A5 sized copy is relveant. 2 sets of rings, two rebuilds, still sooty black and horrible oily looking plugs and occasional smoke after 500 miles... got myself some Mahle branded rings, instructions with them are NICE. said these rings have dots on to show top. My issue. i was using the discussion about profile in the first part of the Sealed Power instructions for my second ring and wondering why it had no dot, so based it all on profile which happend to be a discussion about inner rather than outer.... no discussion of special inner profiles up to this point...Hence second ring upside down twice. It took the mahle instructions to make me take note, and then i could go back and fully understand that the sealed power instructions section i belived was for my rings wasn't and that clear as mud last sentence is read slowly with hindsight and a ring in yoru hand did tell you what you needed to know. I too, had profesionals look at my motor and ended up doing valve guides new stem seals etc. hard lesson learned, and as i had sucessfully built numerouse 2 strokes and VW bug engines over the years from a teenager to my 40s... i felt particularly foolish. i now have a picture on the wall. this profile on the outer side...This way up, and the instructions well they are read afterwards just in case ....

Dave