I would think that the "clicking" is from a lack of a film coating of lubricant sufficient enough to dampen stack up tolerances in the bearings . The blackened areas on the pistons are most likely from some ring leakage but primarily from oil flash of from the high temps. I would lube everything up well and reassemble and the clicking will probably diminish significantly . I would use 30:1 or 40:1 oil ratio for a while with proper tuning to get engine temps down.