valve train noise

[Rancho Deluxe]

Hi Barners
Here's a question I'm puzzeling over. My 30 A Fordor restoration is just about finished with the running chassis. I have a rebuilt engine that seems to run fine now with about two or three total hours of light operation. I'm trying to track down a light to medium tapping noise at valve train speed that has eluded identification. It is not a loose valve clearance . I've checked and reset the tappet clearances three times. They are OK. I can not tell where the noise is coming from with the "Stick to ear" method. but it seems to be from the right side top area in general. I'm not sure whether to move on (and depend on the writer's opinion that these noises either go away by themselves or get worse enough that you can identify them), or to keep at it and fix the problem while everything is exposed and accessible.
What else causes clicky tapping sounds at valve speed? The noise is present in all engine speeds and spark advance settings I've tried. The engine has a reground cam. Can the valve guides create noise by being too loose or even too tight? Aside from checking valve springs and guides, is there anything else that might help diagnose this problem? Thanks to all the barners writing on this topic!
Merry Christmas, Rancho Deluxe