Ticking valvetrain noise from fresh engine

Hey folks,
a long story short: My engine is a 1997 318magnum block in a 69 barracuda, complete rebuild, new rings, new bearings, new valves, new guides, new flat tappet cam 262/268, new hydro lifters, new pushrods, new hughes springs, stock stamped rocker arms on magnum heads. 4bbl intake and tti headers. Broken in with mineral oil, hughes hp additive and cam lube on the lobes, I have done several mopar LA small blocks before)

Did the 20min break-in yesterday, engine had a ticking noise to it after a couple of minutes. It´s hard to hear from the passenger compartment, even hard to hear if you´re next to the car and the hood is closed, but it´s noticable when you open the hood. Sounds brighter than a flat cam lobe. Hardly noticable at idle, noisy at 2000rpm.
Noise is only on the driver´s side bank.
Took off the valve covers, put a stetoscope?!? (hearing aid) onto each of the rocker´s fasteners and found #1ex #3in and #5ex to be the source of the noise.
Exspecting the worst (cam failure), I removed the intake manifold and found all cam lobes to be in perfect shape. Pushrods were fine, Rockers looked great, so I replaced the only suspect left: the lifters
But even with three new lifters (with new oil, additive and cam lube) the noise came back within the first few minutes of the second break-in on the same 1ex 3in 5ex rocker arms.
I´ll get back at it after tomorrow, but I´m out of ideas today... any suggestions what this could be?
Thanks
Chris