Hughes retro hydraulic roller lifters

At the Risk of me sounding like an idiot; are you sure it's the hydraulics causing the noise?
Obviously you have narrowed it down to the valve train. But what about rocker to spring clearance, pushrod to tunnel clearance, or valve to piston clearance? Or even rocker to shaft or rocker to rocker clearance. Or even the link-bars. And finally are the lifters staying deep enough in the lifter bores to not lose their oil-pressure?