I'm assuming it is the lifters. From searching it sounds like it could be noisy injectors, I'll look into that soon. How likely is it that the lifters have dried up from sitting for two years? It goes up and down with the RPM, seems to be consistent with one cylinder's spark timing. Slider cam, 85 287 head, hm....... Recent thread repair on one of the cylinders, but that seems to be a solid fix.
Thoughts?