Thanks for the help and ideas, the obvious ones are definitely of value too. This is my first mopar big block so I still am learning.

I have contacted the builder to see if he can give me any more information on the valvetrain setup. I’ll let you all know what comes out of that.

The thing I see at this point is excessive slop in the pushrods and rocker arms. I’ve done some research here, seems like they should have a bit of preload on them when unloaded, right?
I don’t see any shims or spacers under the rocker shaft mounts. I imagine the pushrods are just not the correct match for the lifters and stock rockers.

That video with the Rhodes lifter sounds pretty much like my engine at idle but I kinda don’t think that’s the issue.

Thanks again. Keep the ideas coming.